v1.0.5

.github/workflows/ci.yml

@@ -115,31 +115,40 @@ jobs:
       matrix:
         include:
           - target: x86_64-unknown-linux-gnu
+            runner: ubuntu-latest
             platform: linux/amd64
             suffix: ""
           - target: x86_64-unknown-linux-musl
+            runner: ubuntu-latest
             platform: linux/amd64
             suffix: "-alpine"
           - target: aarch64-unknown-linux-gnu
+            runner: ubuntu-24.04-arm
             platform: linux/arm64
             suffix: ""
           - target: aarch64-unknown-linux-musl
+            runner: ubuntu-24.04-arm
             platform: linux/arm64
             suffix: "-alpine"
           - target: armv7-unknown-linux-gnueabihf
+            runner: ubuntu-latest
             platform: linux/arm/v7
             suffix: ""
           - target: armv7-unknown-linux-musleabihf
+            runner: ubuntu-latest
             platform: linux/arm/v7
             suffix: "-alpine"
           - target: arm-unknown-linux-gnueabihf
+            runner: ubuntu-latest
             platform: linux/arm/v6
             suffix: ""
           - target: arm-unknown-linux-musleabihf
+            runner: ubuntu-latest
             platform: linux/arm/v6
             suffix: "-alpine"
     name: Build / ${{matrix.target}}
-    runs-on: ubuntu-latest
+    runs-on: ${{matrix.runner}}
+    timeout-minutes: 180
     steps:
       - name: Checkout
         uses: actions/checkout@v7
@@ -155,23 +164,31 @@ jobs:
       - name: Add swap (heavy ARM targets)
         if: contains(matrix.target, 'arm') || contains(matrix.target, 'aarch64')
         run: |
-          mnt_avail=$(df --output=avail -k /mnt | tail -1)
-          if [ "$mnt_avail" -lt 18874368 ]; then
-            echo "Insufficient space on /mnt (${mnt_avail}K available), aborting swap setup"
+          swap_dir=""
+          for dir in /mnt /; do
+            if [ -d "$dir" ] && [ "$(df --output=avail -k "$dir" | tail -1)" -ge 18874368 ]; then
+              swap_dir="$dir"
+              break
+            fi
+          done
+          if [ -z "$swap_dir" ]; then
+            echo "Insufficient space for swap on /mnt or /, aborting swap setup"
+            df -h
             exit 1
           fi
-          sudo fallocate -l 16G /mnt/swapfile
-          sudo chmod 600 /mnt/swapfile
-          sudo mkswap /mnt/swapfile
-          sudo swapon /mnt/swapfile
+          sudo fallocate -l 16G "${swap_dir%/}/swapfile"
+          sudo chmod 600 "${swap_dir%/}/swapfile"
+          sudo mkswap "${swap_dir%/}/swapfile"
+          sudo swapon "${swap_dir%/}/swapfile"
           sudo sysctl vm.swappiness=80
           free -h
           swapon --show
 
       - name: Set up QEMU
+        if: startsWith(matrix.platform, 'linux/arm/')
         uses: docker/setup-qemu-action@v4
         with:
-          platforms: "arm64,arm"
+          platforms: "arm"
 
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v4
@@ -190,6 +207,7 @@ jobs:
           password: ${{github.token}}
 
       - name: Log In to DockerHub
+        if: github.event_name == 'push' || inputs.Docker
         uses: docker/login-action@v4
         with:
           username: ${{secrets.DOCKERHUB_USERNAME}}
@@ -207,7 +225,7 @@ jobs:
           path: |
             var-cache-apt
             var-lib-apt
-          key: apt-cache-${{ hashFiles('Dockerfile.build') }}
+          key: apt-cache-${{ runner.arch }}-${{ hashFiles('Dockerfile.build') }}
 
       - name: Cache Cargo
         uses: actions/cache@v6.1.0
@@ -244,6 +262,7 @@ jobs:
             type=ref,event=branch,prefix=branch-
             type=edge,branch=main
             type=semver,pattern=v{{major}}.{{minor}}
+            type=semver,pattern=v{{major}}
 
       - name: Build Artifact
         id: bake

.gitignore

@@ -3,3 +3,4 @@
 *.md
 !CHANGELOG.md
 !README.md
+__pycache__/

CHANGELOG.md

@@ -2,6 +2,23 @@
 
 All notable changes to this project will be documented in this file. This project adheres to [Semantic Versioning](http://semver.org/).
 
+## [1.0.5] - 2026-10-25
+
+### Added
+
+### Changed
+- Replaced `base64` with `encodify`.
+- An HTTP route's `fallback` is now honoured: unmatched or unmapped requests on that route go to the fallback destination instead of `routing.default_destination`. A `fallback` naming an undeclared destination, or one that does not declare the `http` protocol, is rejected at startup.
+- A login held by `POST /connections/delay` now resolves its destination when the hold ends instead of before it.
+- `PUT /mappings`, `DELETE /mappings` and `POST /cache/invalidate?identifier=` end the login delay of that identifier; `POST /mappings/reload` and `POST /cache/invalidate` without an identifier end every login delay. Held logins proceed at once to the newly mapped destination.
+- Calling `POST /connections/delay` again for an identifier also moves the hold deadline of logins already waiting (still capped at 120 seconds per login).
+
+### Fixed
+- The sample configuration written by `install.sh` and `resources/config.sample.toml` named an undeclared HTTP route fallback (`default`) and failed startup validation.
+- `resources/config.stalwart-upgrade.toml` now documents the WebUI OAuth client identifiers (`https://<host>/admin/oauth-client.json`, `https://<host>/account/oauth-client.json`) and pins `/admin`, `/account`, `/api/auth/**` to the new deployment.
+- The `POST /config/reload` response no longer claims that cache capacity and TTLs require a restart; a reload rebuilds the router and its cache.
+- `POST /connections/delay` with a `seconds` value too large to represent now returns `400` instead of panicking.
+
 ## [1.0.4] - 2026-09-10
 
 ### Added

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "proxy"
-version = "1.0.4"
+version = "1.0.5"
 edition = "2024"
 license = "AGPL-3.0-only OR LicenseRef-SEL"
 description = "Multi-protocol e-mail proxy"
@@ -22,10 +22,9 @@ tokio-rustls = { version = "0.26", default-features = false, features = ["aws_lc
 rustls-pemfile = "2.2"
 rustls-pki-types = "1.15"
 aws-lc-rs = "1.17"
-proxy-header = { version = "0.1.2", features = ["tokio"] }
+proxy-header = { version = "0.1", features = ["tokio"] }
 smtp-proto = "0.2.2"
-mail-parser = "0.11"
-base64 = "0.23"
+encodify = "1.0"
 serde = { version = "1", features = ["derive"] }
 serde_json = "1"
 toml = "1"

Dockerfile.build

@@ -24,19 +24,22 @@ RUN \
     echo 'Binary::apt::APT::Keep-Downloaded-Packages "true";' >/etc/apt/apt.conf.d/keep-cache && \
     apt-get update && \
     apt-get install -yq --no-install-recommends ca-certificates curl git jq xz-utils make libclang-19-dev
-# Zig is pinned to 0.13.0. Zig 0.14+ changed how its default target ABI is
-# resolved for `x86_64-linux-gnu`-style triples, and on this dependency tree
-# (aws-lc-sys, libsqlite3-sys, rust-std 1.87+) that surfaces as ld.lld
-# undefined references to glibc 2.33+ symbols. Zig 0.13 produces binaries with
-# a max glibc ref of ~2.28 which stays compatible with Debian 11 / RHEL 8.
 RUN \
-    ZIG_VERSION=0.13.0 && \
-    curl --retry 5 -fsSL "https://ziglang.org/download/${ZIG_VERSION}/zig-linux-$(uname -m)-${ZIG_VERSION}.tar.xz" | tar -J -x -C /usr/local && \
-    ln -s "/usr/local/zig-linux-$(uname -m)-${ZIG_VERSION}/zig" /usr/local/bin/zig && \
+    ZIG_VERSION=0.17.0 && \
+    case "$(uname -m)" in \
+        x86_64) ZIG_SHA256=1cbe9df9f27e6b78d14ccbca43b6703a404ef79ef1c463de901d7f088d4e2026 ;; \
+        aarch64) ZIG_SHA256=9e8d11661d4ae3bd57702a3832781e23ad151dde5798e16a5ccd503f65234ff8 ;; \
+        *) exit 1 ;; \
+    esac && \
+    curl --retry 5 -fsSLo /tmp/zig.tar.xz "https://ziglang.org/download/${ZIG_VERSION}/zig-$(uname -m)-linux-${ZIG_VERSION}.tar.xz" && \
+    echo "${ZIG_SHA256}  /tmp/zig.tar.xz" | sha256sum -c - && \
+    tar -J -x -C /usr/local -f /tmp/zig.tar.xz && \
+    rm /tmp/zig.tar.xz && \
+    ln -s "/usr/local/zig-$(uname -m)-linux-${ZIG_VERSION}/zig" /usr/local/bin/zig && \
     zig version
 # Install cargo-binstall
 RUN curl --retry 5 -fL --proto '=https' --tlsv1.2 -sSf https://raw.githubusercontent.com/cargo-bins/cargo-binstall/main/install-from-binstall-release.sh | bash
-# Install cargo-chef & sccache & cargo-zigbuild. Versions are pinned so that an
+# Install cargo-chef & sccache. Versions are pinned so that an
 # upstream release without prebuilt binaries for this platform cannot silently
 # turn this into a from-source build, and the `compile` strategy is disabled
 # because that fallback needs an OpenSSL toolchain this image does not carry:
@@ -44,11 +47,12 @@ RUN curl --retry 5 -fL --proto '=https' --tlsv1.2 -sSf https://raw.githubusercon
 RUN \
     for attempt in 1 2 3; do \
         cargo binstall --no-confirm --disable-strategies compile \
-            cargo-chef@0.1.78 sccache@0.17.0 cargo-zigbuild@0.23.2 && break; \
+            cargo-chef@0.1.78 sccache@0.17.0 && break; \
         echo "cargo binstall attempt ${attempt} failed, retrying"; \
         sleep $((attempt * 15)); \
     done && \
-    command -v cargo-chef && command -v sccache && command -v cargo-zigbuild
+    command -v cargo-chef && command -v sccache
+RUN cargo install --locked --git https://github.com/rust-cross/cargo-zigbuild --rev d9f7fd32fbac13cc26d23847835f7f23a5ed3a25 cargo-zigbuild
 
 # *****************
 # Planner
@@ -67,6 +71,7 @@ WORKDIR /app
 COPY --from=planner /app/recipe.json recipe.json
 ARG TARGET
 ARG BUILD_ENV
+ARG GLIBC_VERSION=2.28
 SHELL ["/bin/bash", "-o", "pipefail", "-c"]
 # Install toolchain and specify some env variables
 RUN \
@@ -74,6 +79,13 @@ RUN \
     rustup target add ${TARGET} && \
     mkdir -p artifact && \
     touch /env-cargo && \
+    if [[ "${TARGET}" == *-gnu* ]]; then \
+        echo "export BUILD_TARGET=${TARGET}.${GLIBC_VERSION}" >> /env-cargo; \
+        mkdir -p target && \
+        ln -s "${TARGET}" "target/${TARGET}.${GLIBC_VERSION}"; \
+    else \
+        echo "export BUILD_TARGET=${TARGET}" >> /env-cargo; \
+    fi && \
     if [ ! -z "${BUILD_ENV}" ]; then \
         echo "export ${BUILD_ENV}" >> /env-cargo; \
         echo "Setting up ${BUILD_ENV}"; \
@@ -85,7 +97,7 @@ RUN \
     --mount=type=cache,target=/usr/local/cargo/registry \
     --mount=type=cache,target=/usr/local/cargo/git \
     source /env-cargo && \
-    cargo chef cook --recipe-path recipe.json --zigbuild --release --target ${TARGET} -p proxy
+    cargo chef cook --recipe-path recipe.json --zigbuild --release --target ${BUILD_TARGET} -p proxy
 # Copy the source code
 COPY . .
 ENV RUSTC_WRAPPER="sccache" \
@@ -97,7 +109,7 @@ RUN \
     --mount=type=cache,target=/usr/local/cargo/registry \
     --mount=type=cache,target=/usr/local/cargo/git \
     source /env-cargo && \
-    cargo zigbuild --release --target ${TARGET} -p proxy && \
+    cargo zigbuild --release --target ${BUILD_TARGET} -p proxy && \
     mv /app/target/${TARGET}/release/proxy /app/artifact/proxy
 
 # *****************

install.sh

@@ -266,8 +266,8 @@ tls = "implicit"
 port = 995
 tls = "implicit"
 [destination.stalwart.protocol.submission]
-port = 587
-tls = "starttls"
+port = 465
+tls = "implicit"
 [destination.stalwart.protocol.managesieve]
 port = 4190
 tls = "starttls"
@@ -277,37 +277,37 @@ tls = "implicit"
 
 [listener.imap]
 protocol = "imap"
-bind = ["0.0.0.0:993", "[::]:993"]
+bind = ["[::]:993"]
 tls = "implicit"
 
 [listener.imap-starttls]
 protocol = "imap"
-bind = ["0.0.0.0:143", "[::]:143"]
+bind = ["[::]:143"]
 tls = "starttls"
 
 [listener.pop3]
 protocol = "pop3"
-bind = ["0.0.0.0:995", "[::]:995"]
+bind = ["[::]:995"]
 tls = "implicit"
 
 [listener.submission]
 protocol = "submission"
-bind = ["0.0.0.0:587", "[::]:587"]
+bind = ["[::]:587"]
 tls = "starttls"
 
 [listener.submissions]
 protocol = "submission"
-bind = ["0.0.0.0:465", "[::]:465"]
+bind = ["[::]:465"]
 tls = "implicit"
 
 [listener.managesieve]
 protocol = "managesieve"
-bind = ["0.0.0.0:4190", "[::]:4190"]
+bind = ["[::]:4190"]
 tls = "starttls"
 
 [listener.https]
 protocol = "http"
-bind = ["0.0.0.0:443", "[::]:443"]
+bind = ["[::]:443"]
 tls = "implicit"
 forwarded = "off"
 
@@ -318,7 +318,7 @@ destination = "legacy"
 [[http.route]]
 match = "/**"
 extract = { from = "authorization" }
-fallback = "default"
+fallback = "legacy"
 
 [admin]
 bind = "127.0.0.1:9443"

resources/config.dovecot-postfix.toml

@@ -112,8 +112,8 @@ tls = "implicit"
 port = 995
 tls = "implicit"
 [destination.stalwart.protocol.submission]
-port = 587
-tls = "starttls"
+port = 465
+tls = "implicit"
 [destination.stalwart.protocol.managesieve]
 port = 4190
 tls = "starttls"
@@ -129,38 +129,45 @@ tls = "plain"
 # here. Once accounts are on Stalwart, JMAP and the web interface are served by
 # the new server; an HTTP listener routing to "stalwart" can be added at that
 # point if a single hostname for web access is wanted.
+#
+# Each listener binds [::] only: on Linux and macOS that socket also accepts
+# IPv4 clients, and on Linux a second 0.0.0.0 entry for the same port fails
+# with "Address already in use". Where IPv6 sockets are IPv6-only (FreeBSD by
+# default, or net.ipv6.bindv6only = 1 on Linux), add "0.0.0.0:<port>" to each
+# bind list. On a host whose kernel has IPv6 disabled, [::] cannot be bound:
+# use "0.0.0.0:<port>" instead.
 # ---------------------------------------------------------------------------
 [listener.imaps]
 protocol = "imap"
-bind = ["0.0.0.0:993", "[::]:993"]
+bind = ["[::]:993"]
 tls = "implicit"
 [listener.imap]
 protocol = "imap"
-bind = ["0.0.0.0:143", "[::]:143"]
+bind = ["[::]:143"]
 tls = "starttls"
 [listener.pop3s]
 protocol = "pop3"
-bind = ["0.0.0.0:995", "[::]:995"]
+bind = ["[::]:995"]
 tls = "implicit"
 [listener.pop3]
 protocol = "pop3"
-bind = ["0.0.0.0:110", "[::]:110"]
+bind = ["[::]:110"]
 tls = "starttls"
 [listener.submission]
 protocol = "submission"
-bind = ["0.0.0.0:587", "[::]:587"]
+bind = ["[::]:587"]
 tls = "starttls"
 [listener.submissions]
 protocol = "submission"
-bind = ["0.0.0.0:465", "[::]:465"]
+bind = ["[::]:465"]
 tls = "implicit"
 [listener.managesieve]
 protocol = "managesieve"
-bind = ["0.0.0.0:4190", "[::]:4190"]
+bind = ["[::]:4190"]
 tls = "starttls"
 [listener.smtp]
 protocol = "smtp"
-bind = ["0.0.0.0:25", "[::]:25"]
+bind = ["[::]:25"]
 tls = "plain"
 
 # ---------------------------------------------------------------------------

resources/config.sample.toml

@@ -92,8 +92,8 @@ tls = "implicit"
 port = 995
 tls = "implicit"
 [destination.stalwart.protocol.submission]
-port = 587
-tls = "starttls"
+port = 465
+tls = "implicit"
 [destination.stalwart.protocol.managesieve]
 port = 4190
 tls = "starttls"
@@ -104,40 +104,47 @@ tls = "implicit"
 # ---------------------------------------------------------------------------
 # Listeners: one entry per protocol + TLS mode + bind set.
 # tls = "implicit" | "starttls" | "plain".
+#
+# Each listener binds [::] only: on Linux and macOS that socket also accepts
+# IPv4 clients, and on Linux a second 0.0.0.0 entry for the same port fails
+# with "Address already in use". Where IPv6 sockets are IPv6-only (FreeBSD by
+# default, or net.ipv6.bindv6only = 1 on Linux), add "0.0.0.0:<port>" to each
+# bind list. On a host whose kernel has IPv6 disabled, [::] cannot be bound:
+# use "0.0.0.0:<port>" instead.
 # ---------------------------------------------------------------------------
 [listener.imap]
 protocol = "imap"
-bind = ["0.0.0.0:993", "[::]:993"]
+bind = ["[::]:993"]
 tls = "implicit"
 
 [listener.imap-starttls]
 protocol = "imap"
-bind = ["0.0.0.0:143", "[::]:143"]
+bind = ["[::]:143"]
 tls = "starttls"
 
 [listener.pop3]
 protocol = "pop3"
-bind = ["0.0.0.0:995", "[::]:995"]
+bind = ["[::]:995"]
 tls = "implicit"
 
 [listener.submission]
 protocol = "submission"
-bind = ["0.0.0.0:587", "[::]:587"]
+bind = ["[::]:587"]
 tls = "starttls"
 
 [listener.submissions]
 protocol = "submission"
-bind = ["0.0.0.0:465", "[::]:465"]
+bind = ["[::]:465"]
 tls = "implicit"
 
 [listener.managesieve]
 protocol = "managesieve"
-bind = ["0.0.0.0:4190", "[::]:4190"]
+bind = ["[::]:4190"]
 tls = "starttls"
 
 [listener.https]
 protocol = "http"
-bind = ["0.0.0.0:443", "[::]:443"]
+bind = ["[::]:443"]
 tls = "implicit"
 forwarded = "off"
 
@@ -152,7 +159,7 @@ destination = "legacy"
 [[http.route]]
 match = "/**"
 extract = { from = "authorization" }
-fallback = "default"
+fallback = "legacy"
 
 # ---------------------------------------------------------------------------
 # Admin listener: the cache-integrity boundary. Bind to loopback or a dedicated

resources/config.stalwart-upgrade.toml

@@ -100,8 +100,8 @@ tls = "implicit"
 port = 995
 tls = "implicit"
 [destination.old.protocol.submission]
-port = 587
-tls = "starttls"
+port = 465
+tls = "implicit"
 [destination.old.protocol.managesieve]
 port = 4190
 tls = "starttls"
@@ -124,8 +124,8 @@ tls = "implicit"
 port = 995
 tls = "implicit"
 [destination.new.protocol.submission]
-port = 587
-tls = "starttls"
+port = 465
+tls = "implicit"
 [destination.new.protocol.managesieve]
 port = 4190
 tls = "starttls"
@@ -165,12 +165,21 @@ destination = "old"
 match = "/api/auth"
 destination = "new"
 [[http.route]]
+match = "/api/auth/**"
+destination = "new"
+[[http.route]]
 match = "/api/discover/**"
 destination = "new"
 [[http.route]]
+match = "/admin"
+destination = "new"
+[[http.route]]
 match = "/admin/**"
 destination = "new"
 [[http.route]]
+match = "/account"
+destination = "new"
+[[http.route]]
 match = "/account/**"
 destination = "new"
 [[http.route]]
@@ -181,53 +190,63 @@ match = "/device"
 destination = "new"
 
 # OAuth token exchange is shared; route it by the web client that requested it.
-# Add matching mapping entries:  webadmin  old   and   stalwart-webui  new
+# Add matching mapping entries (replace the hostname with the public one):
+#   webadmin                                             old
+#   https://mail.example.org/admin/oauth-client.json     new
+#   https://mail.example.org/account/oauth-client.json   new
 [[http.route]]
 match = "/auth/token"
 extract = { from = "body", regex = "client_id=([^&]+)" }
 fallback = "old"
 
-# Everything else: route by the authenticated account, fall back to default.
+# Everything else: route by the authenticated account, fall back to the old deployment.
 [[http.route]]
 match = "/**"
 extract = { from = "authorization" }
-fallback = "default"
+fallback = "old"
 
 # ---------------------------------------------------------------------------
 # Listeners: the public ports clients connect to. These take over the ports the
 # old server used to answer on directly.
+#
+# Each listener binds [::] only: on Linux and macOS that socket also accepts
+# IPv4 clients, and on Linux a second 0.0.0.0 entry for the same port fails
+# with "Address already in use". Where IPv6 sockets are IPv6-only (FreeBSD by
+# default, or net.ipv6.bindv6only = 1 on Linux), add "0.0.0.0:<port>" to each
+# bind list. On a host whose kernel has IPv6 disabled, [::] cannot be bound:
+# use "0.0.0.0:<port>" instead.
 # ---------------------------------------------------------------------------
 [listener.imaps]
 protocol = "imap"
-bind = ["0.0.0.0:993", "[::]:993"]
+bind = ["[::]:993"]
 tls = "implicit"
 [listener.imap]
 protocol = "imap"
-bind = ["0.0.0.0:143", "[::]:143"]
+bind = ["[::]:143"]
 tls = "starttls"
 [listener.pop3s]
 protocol = "pop3"
-bind = ["0.0.0.0:995", "[::]:995"]
+bind = ["[::]:995"]
 tls = "implicit"
 [listener.pop3]
 protocol = "pop3"
-bind = ["0.0.0.0:110", "[::]:110"]
+bind = ["[::]:110"]
 tls = "starttls"
 [listener.submission]
 protocol = "submission"
-bind = ["0.0.0.0:587", "[::]:587"]
+bind = ["[::]:587"]
 tls = "starttls"
 [listener.submissions]
 protocol = "submission"
-bind = ["0.0.0.0:465", "[::]:465"]
+bind = ["[::]:465"]
 tls = "implicit"
 [listener.managesieve]
 protocol = "managesieve"
-bind = ["0.0.0.0:4190", "[::]:4190"]
+bind = ["[::]:4190"]
 tls = "starttls"
 [listener.https]
 protocol = "http"
-bind = ["0.0.0.0:443", "[::]:443"]
+bind = ["[::]:443"]
 tls = "implicit"
 # Strip any Forwarded / X-Forwarded-For headers arriving from clients rather
 # than trusting them; the proxy sets its own based on the real peer.
@@ -236,7 +255,7 @@ forwarded = "off"
 # a pass-through listener cannot offer STARTTLS.
 [listener.smtp]
 protocol = "smtp"
-bind = ["0.0.0.0:25", "[::]:25"]
+bind = ["[::]:25"]
 tls = "plain"
 
 # ---------------------------------------------------------------------------

resources/migrate_v016_to_plan.py

@@ -0,0 +1,331 @@
+#!/usr/bin/env python3
+
+import argparse
+import base64
+import json
+import os
+import ssl
+import sys
+import urllib.error
+import urllib.parse
+import urllib.request
+
+REQUEST_TIMEOUT = 60
+DEFAULT_PAGE_SIZE = 500
+MASKED = "****"
+USING = ["urn:ietf:params:jmap:core", "urn:stalwart:jmap"]
+COPIED_FIELDS = ("description", "quotas", "locale", "timeZone")
+
+
+class ApiError(RuntimeError):
+    pass
+
+
+class StalwartV016Client:
+    def __init__(self, url, token=None, username=None, password=None, insecure=False):
+        self.base = url.rstrip("/")
+        if token:
+            self.auth = "Bearer " + token
+        elif username is not None:
+            raw = f"{username}:{password or ''}".encode()
+            self.auth = "Basic " + base64.b64encode(raw).decode()
+        else:
+            raise ValueError("either a token or a username must be provided")
+        self.ctx = None
+        if insecure:
+            self.ctx = ssl.create_default_context()
+            self.ctx.check_hostname = False
+            self.ctx.verify_mode = ssl.CERT_NONE
+        self.api_url = None
+        self.page_size = DEFAULT_PAGE_SIZE
+
+    def request(self, url, body=None):
+        data = json.dumps(body).encode() if body is not None else None
+        req = urllib.request.Request(url, data=data, method="POST" if data else "GET")
+        req.add_header("Authorization", self.auth)
+        req.add_header("Accept", "application/json")
+        if data:
+            req.add_header("Content-Type", "application/json")
+        try:
+            with urllib.request.urlopen(req, timeout=REQUEST_TIMEOUT, context=self.ctx) as resp:
+                return json.loads(resp.read().decode())
+        except urllib.error.HTTPError as exc:
+            detail = exc.read().decode(errors="replace")
+            raise ApiError(f"{exc.code} {exc.reason} for {url}: {detail}") from exc
+        except urllib.error.URLError as exc:
+            raise ApiError(f"cannot reach {url}: {exc.reason}") from exc
+
+    def connect(self):
+        session = self.request(self.base + "/.well-known/jmap")
+        api_url = session.get("apiUrl")
+        if not api_url:
+            raise ApiError("the JMAP session does not advertise an apiUrl")
+        self.api_url = self.base + (urllib.parse.urlsplit(api_url).path or "/jmap")
+        core = (session.get("capabilities") or {}).get("urn:ietf:params:jmap:core") or {}
+        max_get = core.get("maxObjectsInGet")
+        if isinstance(max_get, int) and max_get > 0:
+            self.page_size = min(DEFAULT_PAGE_SIZE, max_get)
+
+    def call(self, method, args):
+        resp = self.request(self.api_url, {"using": USING, "methodCalls": [[method, args, "c0"]]})
+        responses = resp.get("methodResponses") or []
+        if len(responses) != 1:
+            raise ApiError(f"{method}: unexpected response {resp}")
+        name, result, _ = responses[0]
+        if name == "error":
+            raise ApiError(f"{method}: {result.get('type')}: {result.get('description', '')}")
+        return result
+
+    def query_ids(self, obj):
+        ids = []
+        args = {"limit": self.page_size}
+        while True:
+            batch = self.call(f"x:{obj}/query", args).get("ids") or []
+            ids.extend(batch)
+            if len(batch) < self.page_size:
+                return ids
+            args = {"limit": self.page_size, "anchor": batch[-1], "anchorOffset": 1}
+
+    def get_all(self, obj):
+        objects = []
+        ids = self.query_ids(obj)
+        for start in range(0, len(ids), self.page_size):
+            result = self.call(f"x:{obj}/get", {"ids": ids[start : start + self.page_size]})
+            objects.extend(result.get("list") or [])
+        return objects
+
+
+def entries(value):
+    if isinstance(value, list):
+        return value
+    if isinstance(value, dict):
+        return [value[k] for k in sorted(value, key=lambda k: int(k) if k.isdigit() else k)]
+    return []
+
+
+def as_list_map(items):
+    return {str(i): item for i, item in enumerate(items)}
+
+
+def domain_ref(domain):
+    return "domain_" + "".join(c if c.isalnum() else "_" for c in domain)
+
+
+class PlanBuilder:
+    def __init__(self, domains, existing, warn):
+        self.domains = domains
+        self.existing = existing
+        self.warn = warn
+
+    def domain_target(self, domain_id, address, used):
+        name = self.domains.get(domain_id)
+        if name is None:
+            raise ApiError(f"{address}: references unknown domain id {domain_id}")
+        used.add(name)
+        return self.existing.get(name) or ("#" + domain_ref(name))
+
+    def credentials(self, account, address):
+        creds = []
+        skipped = 0
+        for cred in entries(account.get("credentials")):
+            if cred.get("@type") != "Password":
+                skipped += 1
+                continue
+            secret = cred.get("secret")
+            if not secret or secret == MASKED:
+                raise ApiError(
+                    f"{address}: the source returned a masked password; restart it with "
+                    "STALWART_INCLUDE_SECRETS=1 in its environment"
+                )
+            out = {"@type": "Password", "secret": secret}
+            otp = cred.get("otpAuth")
+            if otp and otp != MASKED:
+                out["otpUrl"] = otp
+            for key in ("expiresAt", "allowedIps"):
+                if cred.get(key):
+                    out[key] = cred[key]
+            creds.append(out)
+        if skipped:
+            self.warn(f"{address}: {skipped} app password(s) or API key(s) not migrated")
+        return creds
+
+    def account(self, account, address, used):
+        kind = account.get("@type")
+        out = {
+            "@type": kind,
+            "name": account["name"],
+            "domainId": self.domain_target(account["domainId"], address, used),
+        }
+        for key in COPIED_FIELDS:
+            if account.get(key) not in (None, {}, []):
+                out[key] = account[key]
+
+        if kind == "User":
+            creds = self.credentials(account, address)
+            if creds:
+                out["credentials"] = as_list_map(creds)
+            else:
+                self.warn(f"{address}: no password credential, the account is created without one")
+
+        roles = account.get("roles") or {}
+        if roles.get("@type") == "Custom":
+            fallback = "User" if kind == "User" else "Default"
+            self.warn(f"{address}: custom roles not migrated, assigned the {fallback} roles")
+            out["roles"] = {"@type": fallback}
+        elif roles:
+            out["roles"] = roles
+
+        permissions = account.get("permissions") or {}
+        if permissions.get("@type") in ("Merge", "Replace"):
+            self.warn(f"{address}: account-level permissions copied, check them on the target")
+            out["permissions"] = permissions
+
+        if kind == "User":
+            encryption = account.get("encryptionAtRest") or {}
+            if encryption.get("@type") not in (None, "Disabled"):
+                self.warn(f"{address}: encryption at rest not migrated, the public key must be added again")
+            out["encryptionAtRest"] = {"@type": "Disabled"}
+
+        if account.get("memberGroupIds"):
+            self.warn(f"{address}: group memberships not migrated")
+        if account.get("externalId"):
+            self.warn(f"{address}: external directory identifier not migrated")
+        if account.get("memberTenantId"):
+            self.warn(f"{address}: tenant membership not migrated")
+
+        aliases = []
+        for alias in entries(account.get("aliases")):
+            entry = {
+                "name": alias["name"],
+                "domainId": self.domain_target(alias["domainId"], address, used),
+                "enable": alias.get("enabled", True),
+            }
+            if alias.get("description"):
+                entry["description"] = alias["description"]
+            aliases.append(entry)
+        if aliases:
+            out["aliases"] = as_list_map(aliases)
+        return out
+
+
+def plan_lines(accounts, builder):
+    used = set()
+    value = {}
+    for address, account in accounts:
+        value["acct_" + str(account["id"])] = builder.account(account, address, used)
+    ops = []
+    missing = sorted(d for d in used if d not in builder.existing)
+    if missing:
+        ops.append(
+            {
+                "@type": "upsert",
+                "object": "Domain",
+                "matchOn": ["name"],
+                "value": {domain_ref(d): {"name": d} for d in missing},
+            }
+        )
+    ops.append({"@type": "create", "object": "Account", "value": value})
+    return [json.dumps(op) for op in ops]
+
+
+def write_lines(path, lines):
+    fd = os.open(path, os.O_WRONLY | os.O_CREAT | os.O_TRUNC, 0o600)
+    with os.fdopen(fd, "w") as out:
+        for line in lines:
+            out.write(line + "\n")
+
+
+def main():
+    parser = argparse.ArgumentParser(
+        description="Build Stalwart CLI plans that recreate the accounts of a Stalwart "
+        "v0.16.27 server, with their password hashes, on a Stalwart v1 server.",
+    )
+    parser.add_argument("addresses", nargs="*", help="export only these accounts (default: all)")
+    parser.add_argument("--url", required=True, help="base URL of the v0.16 server")
+    parser.add_argument("--token", help="admin bearer token")
+    parser.add_argument("--user", help="admin username (HTTP basic auth)")
+    parser.add_argument("--password", help="admin password (default: $SOURCE_ADMIN_PASSWORD)")
+    parser.add_argument("--insecure", action="store_true", help="skip TLS verification")
+    parser.add_argument("--include-groups", action="store_true", help="also export groups")
+    parser.add_argument(
+        "--existing-domain",
+        action="append",
+        default=[],
+        metavar="NAME=ID",
+        help="reference a target domain by id instead of matching it by name",
+    )
+    target = parser.add_mutually_exclusive_group()
+    target.add_argument("--output", help="write one plan to this file (default: stdout)")
+    target.add_argument("--output-dir", help="write one plan per account into this directory")
+    args = parser.parse_args()
+
+    if not args.token and args.user is None:
+        parser.error("provide --token or --user")
+    password = args.password if args.password is not None else os.environ.get("SOURCE_ADMIN_PASSWORD")
+
+    existing = {}
+    for entry in args.existing_domain:
+        name, sep, value = entry.partition("=")
+        if not sep:
+            parser.error(f"--existing-domain expects NAME=ID, got {entry!r}")
+        existing[name.strip().lower()] = value.strip()
+
+    client = StalwartV016Client(
+        args.url, token=args.token, username=args.user, password=password, insecure=args.insecure
+    )
+    client.connect()
+
+    domains = {d["id"]: d["name"].lower() for d in client.get_all("Domain")}
+    kinds = {"User", "Group"} if args.include_groups else {"User"}
+    accounts = {}
+    for account in client.get_all("Account"):
+        if account.get("@type") not in kinds:
+            continue
+        domain = domains.get(account.get("domainId"))
+        if domain:
+            accounts[f"{account['name']}@{domain}".lower()] = account
+
+    if args.addresses:
+        wanted = [a.lower() for a in args.addresses]
+        unknown = [a for a in wanted if a not in accounts]
+        if unknown:
+            sys.stderr.write("unknown account(s): " + ", ".join(unknown) + "\n")
+            return 1
+        selected = [(a, accounts[a]) for a in wanted]
+    else:
+        selected = sorted(accounts.items())
+
+    if not selected:
+        sys.stderr.write("no accounts to export\n")
+        return 1
+
+    warnings = []
+    builder = PlanBuilder(domains, existing, warnings.append)
+
+    if args.output_dir:
+        os.makedirs(args.output_dir, mode=0o700, exist_ok=True)
+        for address, account in selected:
+            write_lines(
+                os.path.join(args.output_dir, address + ".ndjson"),
+                plan_lines([(address, account)], builder),
+            )
+    else:
+        lines = plan_lines(selected, builder)
+        if args.output:
+            write_lines(args.output, lines)
+        else:
+            for line in lines:
+                sys.stdout.write(line + "\n")
+
+    for warning in warnings:
+        sys.stderr.write("warning: " + warning + "\n")
+    sys.stderr.write(f"exported {len(selected)} account(s)\n")
+    return 0
+
+
+if __name__ == "__main__":
+    try:
+        sys.exit(main())
+    except ApiError as exc:
+        sys.stderr.write(f"error: {exc}\n")
+        sys.exit(1)

src/admin.rs

@@ -303,6 +303,7 @@ async fn handle(
                     } else {
                         match ctx.router.upsert(&id, &dest).await {
                             Ok(()) => {
+                                ctx.conns.release_delay(&ctx.router.normalize(&id));
                                 tracing::info!(identifier = %crate::observe::redact(&id), %dest, "admin upserted mapping");
                                 write_response(&mut stream, 200, "OK", "ok\n").await?;
                             }
@@ -343,6 +344,7 @@ async fn handle(
                 } else {
                     match ctx.router.remove(&id).await {
                         Ok(existed) => {
+                            ctx.conns.release_delay(&ctx.router.normalize(&id));
                             tracing::info!(identifier = %crate::observe::redact(&id), existed, "admin removed mapping");
                             let body = if existed { "removed\n" } else { "absent\n" };
                             write_response(&mut stream, 200, "OK", body).await?;
@@ -379,7 +381,7 @@ async fn handle(
                     tracing::info!("admin reloaded configuration");
                     let body = serde_json::json!({
                         "reloaded": true,
-                        "note": "listener binds/protocols, admin bind/token, and cache capacity/TTLs require a restart to change",
+                        "note": "listener binds/protocols and admin bind/token require a restart to change",
                     })
                     .to_string();
                     write_json(&mut stream, 200, &body).await?;
@@ -400,10 +402,12 @@ async fn handle(
             match request.query_param("identifier") {
                 Some(id) => {
                     ctx.router.invalidate(&id).await;
+                    ctx.conns.release_delay(&ctx.router.normalize(&id));
                     tracing::info!(identifier = %crate::observe::redact(&id), "admin invalidated entry");
                 }
                 None => {
                     ctx.router.invalidate_all();
+                    ctx.conns.release_all_delays();
                     tracing::info!("admin invalidated entire cache");
                 }
             }
@@ -411,6 +415,7 @@ async fn handle(
         }
         ("POST", "/mappings/reload") => match ctx.router.reload().await {
             Ok(()) => {
+                ctx.conns.release_all_delays();
                 tracing::info!("admin reloaded mappings");
                 write_response(&mut stream, 200, "OK", "reloaded\n").await?;
             }
@@ -435,15 +440,17 @@ async fn handle(
                 request.query_param("identifier"),
                 request.query_param("seconds"),
             ) {
-                (Some(id), Some(secs)) => match secs.parse::<u64>() {
-                    Ok(seconds) => {
-                        let until =
-                            std::time::Instant::now() + std::time::Duration::from_secs(seconds);
+                (Some(id), Some(secs)) => match secs.parse::<u64>().ok().and_then(|seconds| {
+                    std::time::Instant::now()
+                        .checked_add(std::time::Duration::from_secs(seconds))
+                        .map(|until| (seconds, until))
+                }) {
+                    Some((seconds, until)) => {
                         ctx.conns.set_delay(&ctx.router.normalize(&id), until);
                         tracing::info!(identifier = %crate::observe::redact(&id), seconds, "admin set login delay");
                         write_response(&mut stream, 200, "OK", "ok\n").await?;
                     }
-                    Err(_) => {
+                    None => {
                         write_response(&mut stream, 400, "Bad Request", "invalid seconds\n")
                             .await?;
                     }

src/config/mod.rs

@@ -920,6 +920,14 @@ impl Config {
                     )));
                 }
             }
+            if let Some(fallback) = &route.fallback {
+                let dest = self.destination(fallback)?;
+                if !dest.protocol.contains_key(&Protocol::Http) {
+                    return Err(ProxyError::config(format!(
+                        "http route fallback {fallback:?} does not declare the http protocol"
+                    )));
+                }
+            }
             if let Some(extract) = &route.extract {
                 if extract.from == ExtractFrom::Body && extract.regex.is_none() {
                     return Err(ProxyError::config(

src/http/proxy.rs

@@ -5,6 +5,7 @@
  */
 
 use std::net::{IpAddr, SocketAddr};
+use std::sync::Arc;
 use std::time::Duration;
 
 use tokio::io::{AsyncReadExt, AsyncWriteExt};
@@ -521,11 +522,7 @@ async fn serve(
     let mut first_head = first_head;
     sanitize_inbound_forwarded(&mut first_head, listener);
 
-    let Prepared {
-        body: buffered_body,
-        dest_id,
-        identifier,
-    } = match prepare(
+    let prepared = match prepare(
         ctx,
         router,
         stream,
@@ -544,9 +541,11 @@ async fn serve(
     };
 
     let mut account = Account::new(cancel);
-    if account.pin(ctx, identifier.as_deref()) {
-        crate::proto::common::hold_login(ctx, identifier.as_deref()).await;
+    if account.pin(ctx, prepared.identifier.as_deref()) {
+        crate::proto::common::hold_login(ctx, prepared.identifier.as_deref()).await;
     }
+    let dest_id = prepared.destination(ctx).await;
+    let buffered_body = prepared.body;
 
     let (dest, ep, tls_cfg) = match ctx.endpoint(&dest_id, Protocol::Http) {
         Ok(t) => t,
@@ -648,11 +647,7 @@ async fn serve(
         let mut next = next;
         sanitize_inbound_forwarded(&mut next, listener);
 
-        let Prepared {
-            body: next_body,
-            dest_id: next_dest,
-            identifier: next_identifier,
-        } = match prepare(
+        let prepared = match prepare(
             ctx,
             router,
             stream,
@@ -670,7 +665,14 @@ async fn serve(
             }
         };
 
-        if next_dest != dest_id || !account.accepts(ctx, next_identifier.as_deref()) {
+        let misdirected = !account.accepts(ctx, prepared.identifier.as_deref()) || {
+            if account.pin(ctx, prepared.identifier.as_deref()) {
+                crate::proto::common::hold_login(ctx, prepared.identifier.as_deref()).await;
+            }
+            prepared.destination(ctx).await != dest_id
+        };
+        let next_body = prepared.body;
+        if misdirected {
             if let Some(body) = &next_body {
                 drain_buffered(stream, &mut reader, &next, body.len(), idle.body)
                     .await
@@ -679,9 +681,6 @@ async fn serve(
             let _ = write_client(stream, &error_response(421, "Misdirected Request")).await;
             return Ok(Disposition::Close);
         }
-        if account.pin(ctx, next_identifier.as_deref()) {
-            crate::proto::common::hold_login(ctx, next_identifier.as_deref()).await;
-        }
 
         current_head = next;
         current_body = next_body;
@@ -970,12 +969,34 @@ async fn drain_buffered(
     Ok(())
 }
 
+enum Target {
+    Pinned(String),
+    Account { fallback: Option<Arc<str>> },
+}
+
 struct Prepared {
     body: Option<Vec<u8>>,
-    dest_id: String,
+    target: Target,
     identifier: Option<String>,
 }
 
+impl Prepared {
+    async fn destination(&self, ctx: &Ctx) -> String {
+        match &self.target {
+            Target::Pinned(dest_id) => dest_id.clone(),
+            Target::Account {
+                fallback: Some(fallback),
+            } => ctx
+                .resolve_or(self.identifier.as_deref(), fallback)
+                .await
+                .to_string(),
+            Target::Account { fallback: None } => {
+                ctx.resolve(self.identifier.as_deref()).await.to_string()
+            }
+        }
+    }
+}
+
 async fn prepare(
     ctx: &Ctx,
     router: &HttpRouter,
@@ -1000,25 +1021,20 @@ async fn prepare(
         None
     };
 
-    let (dest_id, identifier) = match router.route_at(idx, head, body.as_deref()) {
-        RouteOutcome::Pin { dest_id } => (dest_id, None),
+    let (target, identifier) = match router.route_at(idx, head, body.as_deref()) {
+        RouteOutcome::Pin { dest_id } => (Target::Pinned(dest_id), None),
         RouteOutcome::Identifier {
             identifier,
             fallback,
-        } => {
-            let identifier = ctx.routing_identifier(identifier);
-            let dest_id = if identifier.is_none() && fallback.is_none() {
-                ctx.resolve(None).await.to_string()
-            } else {
-                ctx.resolve(identifier.as_deref()).await.to_string()
-            };
-            (dest_id, identifier)
-        }
+        } => (
+            Target::Account { fallback },
+            ctx.routing_identifier(identifier),
+        ),
     };
 
     Ok(Some(Prepared {
         body,
-        dest_id,
+        target,
         identifier,
     }))
 }

src/http/router.rs

@@ -4,9 +4,10 @@
  * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-SEL
  */
 
+use std::sync::Arc;
 use std::time::Duration;
 
-use base64::{Engine, engine::general_purpose::STANDARD as BASE64};
+use encodify::base64::STANDARD as BASE64;
 use globset::{Glob, GlobSet, GlobSetBuilder};
 use regex::Regex;
 
@@ -21,7 +22,7 @@ pub enum RouteOutcome {
     },
     Identifier {
         identifier: Option<String>,
-        fallback: Option<String>,
+        fallback: Option<Arc<str>>,
     },
 }
 
@@ -35,7 +36,7 @@ struct CompiledExtract {
 struct CompiledRoute {
     destination: Option<String>,
     extract: Option<CompiledExtract>,
-    fallback: Option<String>,
+    fallback: Option<Arc<str>>,
     needs_body: bool,
 }
 
@@ -144,8 +145,7 @@ impl HttpRouter {
         let value = head.header("authorization")?;
         let value = value.trim();
         if let Some(rest) = strip_scheme(value, "basic") {
-            let decoded = BASE64.decode(rest.trim()).ok()?;
-            let text = String::from_utf8(decoded).ok()?;
+            let text = BASE64.decode_to_string(rest.trim()).ok()?;
             let login = match text.split_once(':') {
                 Some((login, _)) => login,
                 None => text.as_str(),
@@ -186,7 +186,7 @@ fn compile_route(route: &HttpRoute) -> Result<CompiledRoute> {
     Ok(CompiledRoute {
         destination: route.destination.clone(),
         extract,
-        fallback: route.fallback.clone(),
+        fallback: route.fallback.as_deref().map(Arc::from),
         needs_body,
     })
 }
@@ -320,7 +320,7 @@ destination = "legacy"
 [[route]]
 match = "/**"
 extract = { from = "authorization" }
-fallback = "default"
+fallback = "legacy"
 "#,
         );
         let head = parse(b"GET /static HTTP/1.1\r\nHost: x\r\n\r\n");
@@ -331,7 +331,7 @@ fallback = "default"
         let head = parse(b"GET /dyn HTTP/1.1\r\nHost: x\r\n\r\n");
         match route(&router, &head, None) {
             RouteOutcome::Identifier { fallback, .. } => {
-                assert_eq!(fallback.as_deref(), Some("default"));
+                assert_eq!(fallback.as_deref(), Some("legacy"));
             }
             _ => panic!("expected identifier"),
         }
@@ -359,7 +359,7 @@ extract = { from = "authorization" }
 
     #[test]
     fn bearer_uses_bearer_identifier() {
-        use base64::engine::general_purpose::URL_SAFE_NO_PAD;
+        use encodify::base64::URL_SAFE_NO_PAD;
         let router = router_from_toml(
             r#"
 [[route]]

src/proto/common.rs

@@ -23,7 +23,7 @@ use crate::error::{ProxyError, Result};
 use crate::imap_receiver::Mechanism;
 use crate::net::BoxedStream;
 use crate::net::tls;
-use crate::sasl::Credential;
+use crate::sasl::{Credential, SASL_RESPONSE};
 
 pub struct Handoff {
     pub stream: BoxedStream,
@@ -133,13 +133,15 @@ pub fn sasl_cancelled(response: &[u8]) -> bool {
 }
 
 pub fn login_challenge(username_b64: &[u8], password_b64: &[u8]) -> Option<Vec<u8>> {
-    let username = crate::sasl::decode_sasl_ir(username_b64)?;
-    let password = crate::sasl::decode_sasl_ir(password_b64)?;
-    let mut raw = Vec::with_capacity(username.len() + password.len() + 2);
+    let mut raw = Vec::with_capacity(
+        SASL_RESPONSE.decoded_len_estimate(username_b64.len())
+            + SASL_RESPONSE.decoded_len_estimate(password_b64.len())
+            + 2,
+    );
     raw.push(0);
-    raw.extend_from_slice(&username);
+    SASL_RESPONSE.decode_append(username_b64, &mut raw).ok()?;
     raw.push(0);
-    raw.extend_from_slice(&password);
+    SASL_RESPONSE.decode_append(password_b64, &mut raw).ok()?;
     Some(raw)
 }
 
@@ -293,16 +295,22 @@ pub struct HealthSnapshot {
 }
 
 const REGISTRY_SHARDS: usize = 32;
+const MAX_LOGIN_HOLD: Duration = Duration::from_secs(120);
 
 struct LiveConn {
     id: u64,
     cancel: tokio::sync::watch::Sender<bool>,
 }
 
+struct LoginDelay {
+    until: Instant,
+    changed: tokio::sync::watch::Sender<()>,
+}
+
 #[derive(Default)]
 struct Shard {
     live: HashMap<Arc<str>, Vec<LiveConn>>,
-    delays: HashMap<Arc<str>, Instant>,
+    delays: HashMap<Arc<str>, LoginDelay>,
 }
 
 #[derive(Clone)]
@@ -396,21 +404,64 @@ impl ConnRegistry {
     pub fn set_delay(&self, identifier: &str, until: Instant) {
         let mut shard = self.shards[self.shard_idx(identifier)].lock();
         let now = Instant::now();
-        shard.delays.retain(|_, &mut u| u > now);
-        shard.delays.insert(Arc::from(identifier), until);
+        shard.delays.retain(|_, delay| delay.until > now);
+        match shard.delays.get_mut(identifier) {
+            Some(delay) => {
+                delay.until = until;
+                delay.changed.send_replace(());
+            }
+            None => {
+                shard.delays.insert(
+                    Arc::from(identifier),
+                    LoginDelay {
+                        until,
+                        changed: tokio::sync::watch::Sender::new(()),
+                    },
+                );
+            }
+        }
     }
 
-    pub fn delay_remaining(&self, identifier: &str) -> Option<Duration> {
+    fn delay(&self, identifier: &str) -> Option<(Instant, tokio::sync::watch::Receiver<()>)> {
         let mut shard = self.shards[self.shard_idx(identifier)].lock();
-        if let Some(&until) = shard.delays.get(identifier) {
-            let now = Instant::now();
-            if now < until {
-                return Some(until - now);
-            }
-            shard.delays.remove(identifier);
+        let delay = shard.delays.get(identifier)?;
+        if Instant::now() < delay.until {
+            return Some((delay.until, delay.changed.subscribe()));
         }
+        shard.delays.remove(identifier);
         None
     }
+
+    pub fn release_delay(&self, identifier: &str) {
+        self.shards[self.shard_idx(identifier)]
+            .lock()
+            .delays
+            .remove(identifier);
+    }
+
+    pub fn release_all_delays(&self) {
+        for shard in self.shards.iter() {
+            shard.lock().delays.clear();
+        }
+    }
+
+    pub async fn hold_login(&self, identifier: &str) {
+        let deadline = Instant::now() + MAX_LOGIN_HOLD;
+        while let Some((until, mut changed)) = self.delay(identifier) {
+            let wake = until.min(deadline);
+            if Instant::now() >= wake {
+                break;
+            }
+            tracing::debug!(
+                hold_ms = wake.saturating_duration_since(Instant::now()).as_millis() as u64,
+                "holding login (delay_until)"
+            );
+            tokio::select! {
+                _ = tokio::time::sleep_until(wake.into()) => {}
+                _ = changed.changed() => {}
+            }
+        }
+    }
 }
 
 impl ConnGuard {
@@ -543,6 +594,10 @@ impl Ctx {
         self.router.resolve(identifier).await
     }
 
+    pub async fn resolve_or(&self, identifier: Option<&str>, default: &Arc<str>) -> Arc<str> {
+        self.router.resolve_or(identifier, default).await
+    }
+
     pub fn register_conn(&self, identifier: &str) -> ConnGuard {
         self.conns.register(&self.router.normalize(identifier))
     }
@@ -655,15 +710,8 @@ where
 }
 
 pub async fn hold_login(ctx: &Ctx, identifier: Option<&str>) {
-    if let Some(id) = identifier
-        && let Some(remaining) = ctx.conns.delay_remaining(&ctx.router.normalize(id))
-    {
-        let capped = remaining.min(Duration::from_secs(120));
-        tracing::debug!(
-            hold_ms = capped.as_millis() as u64,
-            "holding login (delay_until)"
-        );
-        tokio::time::sleep(capped).await;
+    if let Some(id) = identifier {
+        ctx.conns.hold_login(&ctx.router.normalize(id)).await;
     }
 }
 
@@ -1114,7 +1162,7 @@ mod tests {
 
     #[test]
     fn login_challenge_builds_a_plain_authentication_frame() {
-        use base64::{Engine, engine::general_purpose::STANDARD as BASE64};
+        use encodify::base64::STANDARD as BASE64;
         let user = BASE64.encode("user@example.com");
         let pass = BASE64.encode("secret");
         assert_eq!(
@@ -1365,14 +1413,86 @@ mod tests {
         assert_eq!(reg.kick("user@example.com"), 0);
     }
 
+    #[tokio::test]
+    async fn conn_registry_release_ends_hold() {
+        // releasing a delay wakes a held login immediately
+        let reg = ConnRegistry::default();
+        reg.set_delay("user@example.com", Instant::now() + Duration::from_secs(60));
+        let held = reg.clone();
+        let hold = tokio::spawn(async move { held.hold_login("user@example.com").await });
+        tokio::time::sleep(Duration::from_millis(50)).await;
+        assert!(!hold.is_finished());
+        reg.release_delay("user@example.com");
+        tokio::time::timeout(Duration::from_secs(2), hold)
+            .await
+            .expect("release did not end the hold")
+            .unwrap();
+        assert!(reg.delay("user@example.com").is_none());
+    }
+
+    #[tokio::test]
+    async fn conn_registry_release_all_ends_holds() {
+        // releasing every delay wakes all held logins
+        let reg = ConnRegistry::default();
+        let until = Instant::now() + Duration::from_secs(60);
+        reg.set_delay("a@example.com", until);
+        reg.set_delay("b@example.com", until);
+        let holds = ["a@example.com", "b@example.com"].map(|id| {
+            let held = reg.clone();
+            tokio::spawn(async move { held.hold_login(id).await })
+        });
+        tokio::time::sleep(Duration::from_millis(50)).await;
+        reg.release_all_delays();
+        for hold in holds {
+            tokio::time::timeout(Duration::from_secs(2), hold)
+                .await
+                .expect("release did not end the hold")
+                .unwrap();
+        }
+    }
+
+    #[tokio::test]
+    async fn conn_registry_shortened_delay_ends_hold() {
+        // shortening a delay wakes a held login at the new deadline
+        let reg = ConnRegistry::default();
+        reg.set_delay("user@example.com", Instant::now() + Duration::from_secs(60));
+        let held = reg.clone();
+        let hold = tokio::spawn(async move { held.hold_login("user@example.com").await });
+        tokio::time::sleep(Duration::from_millis(50)).await;
+        reg.set_delay("user@example.com", Instant::now());
+        tokio::time::timeout(Duration::from_secs(2), hold)
+            .await
+            .expect("shortened delay did not end the hold")
+            .unwrap();
+    }
+
+    #[tokio::test]
+    async fn conn_registry_extended_delay_keeps_hold() {
+        // extending a delay keeps a held login waiting past the original deadline
+        let reg = ConnRegistry::default();
+        reg.set_delay(
+            "user@example.com",
+            Instant::now() + Duration::from_millis(100),
+        );
+        let held = reg.clone();
+        let started = Instant::now();
+        let hold = tokio::spawn(async move { held.hold_login("user@example.com").await });
+        reg.set_delay(
+            "user@example.com",
+            Instant::now() + Duration::from_millis(400),
+        );
+        hold.await.unwrap();
+        assert!(started.elapsed() >= Duration::from_millis(350));
+    }
+
     #[test]
     fn conn_registry_delay_window() {
         let reg = ConnRegistry::default();
-        assert!(reg.delay_remaining("user@example.com").is_none());
+        assert!(reg.delay("user@example.com").is_none());
         reg.set_delay("user@example.com", Instant::now() + Duration::from_secs(30));
-        assert!(reg.delay_remaining("user@example.com").is_some());
+        assert!(reg.delay("user@example.com").is_some());
         reg.set_delay("user@example.com", Instant::now());
-        assert!(reg.delay_remaining("user@example.com").is_none());
+        assert!(reg.delay("user@example.com").is_none());
     }
 
     #[test]

src/proto/imap.rs

@@ -6,7 +6,7 @@
 
 use std::net::SocketAddr;
 
-use base64::{Engine, engine::general_purpose::STANDARD as BASE64};
+use encodify::base64::STANDARD as BASE64;
 use tokio::io::AsyncReadExt;
 use tokio::time::timeout;
 
@@ -19,7 +19,7 @@ use crate::proto::common::{
     self, Ctx, assert_egress_encrypted, mechanism_name, plain_auth_allowed, read_crlf_line, write,
 };
 use crate::proto::forward;
-use crate::sasl::decode_sasl_ir;
+use crate::sasl::SASL_RESPONSE;
 use crate::token::identifier_from_credential;
 
 const MAX_PREAUTH: usize = 64 * 1024;
@@ -82,24 +82,25 @@ pub async fn handle(
         };
 
         let identifier = ctx.routing_identifier(identifier);
-        let dest_id = ctx.resolve(identifier.as_deref()).await;
-        tracing::debug!(destination = %dest_id, "imap routing decision");
-
         let started = std::time::Instant::now();
         common::hold_login(ctx, identifier.as_deref()).await;
+        let dest_id = ctx.resolve(identifier.as_deref()).await;
+        tracing::debug!(destination = %dest_id, "imap routing decision");
 
         let client_tls = client.is_tls();
         let fwd =
             forward::ForwardInfo::new(peer, local, client_tls, None, ctx.config.server.proxy_ttl);
 
         let mech_name = mechanism_name(&mech);
-        let response = BASE64.encode(&raw_challenge);
+        let mut response = String::with_capacity(BASE64.encoded_len(raw_challenge.len()) + 2);
+        BASE64.encode_append(&raw_challenge, &mut response);
+        response.push_str("\r\n");
         let auth = common::AuthFrame::inline(
-            format!("{tag} AUTHENTICATE {mech_name} {response}\r\n").into_bytes(),
+            format!("{tag} AUTHENTICATE {mech_name} {response}").into_bytes(),
         )
         .with_deferred(
             format!("{tag} AUTHENTICATE {mech_name}\r\n").into_bytes(),
-            format!("{response}\r\n").into_bytes(),
+            response.into_bytes(),
         );
         let unavailable = format!("{tag} NO [UNAVAILABLE] backend unavailable\r\n");
 
@@ -404,7 +405,7 @@ impl Auth<'_> {
             read_crlf_line(stream, seed, MAX_PREAUTH).await?
         };
 
-        let Some(raw) = decode_sasl_ir(&raw_b64) else {
+        let Ok(raw) = SASL_RESPONSE.decode(&raw_b64) else {
             return self
                 .reject(
                     stream,

src/proto/managesieve.rs

@@ -6,7 +6,7 @@
 
 use std::net::SocketAddr;
 
-use base64::{Engine, engine::general_purpose::STANDARD as BASE64};
+use encodify::base64::STANDARD as BASE64;
 use tokio::io::AsyncReadExt;
 use tokio::time::timeout;
 
@@ -20,7 +20,7 @@ use crate::proto::common::{
     plain_auth_allowed, write,
 };
 use crate::proto::forward;
-use crate::sasl::decode_sasl_ir;
+use crate::sasl::SASL_RESPONSE;
 use crate::token::identifier_from_credential;
 
 const MAX_PREAUTH: usize = 64 * 1024;
@@ -70,9 +70,9 @@ pub async fn handle(
         } = handoff;
 
         let identifier = ctx.routing_identifier(identifier);
-        let dest_id = ctx.resolve(identifier.as_deref()).await;
         let started = std::time::Instant::now();
         common::hold_login(ctx, identifier.as_deref()).await;
+        let dest_id = ctx.resolve(identifier.as_deref()).await;
         let fwd = forward::ForwardInfo::new(
             peer,
             local,
@@ -81,14 +81,10 @@ pub async fn handle(
             ctx.config.server.proxy_ttl,
         );
 
-        let auth = common::AuthFrame::inline(
-            format!(
-                "AUTHENTICATE \"{}\" \"{}\"\r\n",
-                mechanism_name(&mech),
-                BASE64.encode(&raw_challenge)
-            )
-            .into_bytes(),
-        );
+        let mut frame = format!("AUTHENTICATE \"{}\" \"", mechanism_name(&mech));
+        BASE64.encode_append(&raw_challenge, &mut frame);
+        frame.push_str("\"\r\n");
+        let auth = common::AuthFrame::inline(frame.into_bytes());
 
         let resume = common::bridge_authenticated(
             ctx,
@@ -333,7 +329,7 @@ async fn handle_authenticate(
         read_sasl_response(stream, seed).await?
     };
 
-    let Some(raw) = decode_sasl_ir(&raw_b64) else {
+    let Ok(raw) = SASL_RESPONSE.decode(&raw_b64) else {
         return fail(
             stream,
             "Invalid base64",

src/proto/pop3.rs

@@ -6,7 +6,7 @@
 
 use std::net::SocketAddr;
 
-use base64::{Engine, engine::general_purpose::STANDARD as BASE64};
+use encodify::base64::STANDARD as BASE64;
 use tokio::time::timeout;
 
 use crate::config::{Forwarding, ListenerConfig, Pop3Capabilities, Protocol, TlsMode};
@@ -19,7 +19,7 @@ use crate::proto::common::{
     plain_auth_allowed, write,
 };
 use crate::proto::forward;
-use crate::sasl::decode_sasl_ir;
+use crate::sasl::SASL_RESPONSE;
 use crate::token::identifier_from_credential;
 
 const MAX_PREAUTH: usize = 64 * 1024;
@@ -60,9 +60,9 @@ pub async fn handle(
         } = handoff;
 
         let identifier = ctx.routing_identifier(identifier);
-        let dest_id = ctx.resolve(identifier.as_deref()).await;
         let started = std::time::Instant::now();
         common::hold_login(ctx, identifier.as_deref()).await;
+        let dest_id = ctx.resolve(identifier.as_deref()).await;
         let fwd = forward::ForwardInfo::new(
             peer,
             local,
@@ -71,14 +71,10 @@ pub async fn handle(
             ctx.config.server.proxy_ttl,
         );
 
-        let auth = common::AuthFrame::inline(
-            format!(
-                "AUTH {} {}\r\n",
-                mechanism_name(&mech),
-                BASE64.encode(&raw_challenge)
-            )
-            .into_bytes(),
-        );
+        let mut frame = format!("AUTH {} ", mechanism_name(&mech));
+        BASE64.encode_append(&raw_challenge, &mut frame);
+        frame.push_str("\r\n");
+        let auth = common::AuthFrame::inline(frame.into_bytes());
 
         let resume = common::bridge_authenticated(
             ctx,
@@ -338,7 +334,7 @@ async fn preauth(
                     line
                 };
 
-                let Some(raw) = decode_sasl_ir(&raw_b64) else {
+                let Ok(raw) = SASL_RESPONSE.decode(&raw_b64) else {
                     write(&mut stream, b"-ERR invalid base64\r\n").await?;
                     if bump(auth_failures, listener.max_auth_attempts) {
                         return Ok(None);

src/proto/smtp.rs

@@ -6,7 +6,7 @@
 
 use std::net::SocketAddr;
 
-use base64::{Engine, engine::general_purpose::STANDARD as BASE64};
+use encodify::base64::STANDARD as BASE64;
 use smtp_proto::{
     AUTH_LOGIN, AUTH_OAUTHBEARER, AUTH_PLAIN, AUTH_XOAUTH2, Error as SmtpError, Request,
 };
@@ -22,7 +22,7 @@ use crate::proto::common::{
     plain_auth_allowed, write,
 };
 use crate::proto::forward;
-use crate::sasl::decode_sasl_ir;
+use crate::sasl::SASL_RESPONSE;
 use crate::token::identifier_from_credential;
 
 const MAX_PREAUTH: usize = 64 * 1024;
@@ -92,9 +92,9 @@ pub async fn handle_submission(
         } = handoff;
 
         let identifier = ctx.routing_identifier(identifier);
-        let dest_id = ctx.resolve(identifier.as_deref()).await;
         let started = std::time::Instant::now();
         common::hold_login(ctx, identifier.as_deref()).await;
+        let dest_id = ctx.resolve(identifier.as_deref()).await;
         let fwd = forward::ForwardInfo::new(
             peer,
             local,
@@ -103,14 +103,10 @@ pub async fn handle_submission(
             ctx.config.server.proxy_ttl,
         );
 
-        let auth = common::AuthFrame::inline(
-            format!(
-                "AUTH {} {}\r\n",
-                mechanism_name(&mech),
-                BASE64.encode(&raw_challenge)
-            )
-            .into_bytes(),
-        );
+        let mut frame = format!("AUTH {} ", mechanism_name(&mech));
+        BASE64.encode_append(&raw_challenge, &mut frame);
+        frame.push_str("\r\n");
+        let auth = common::AuthFrame::inline(frame.into_bytes());
 
         let resume = common::bridge_authenticated(
             ctx,
@@ -370,7 +366,7 @@ async fn handle_auth(
         line
     };
 
-    let Some(raw) = decode_sasl_ir(&raw_b64) else {
+    let Ok(raw) = SASL_RESPONSE.decode(&raw_b64) else {
         return fail(
             stream,
             buf,

src/route/mod.rs

@@ -164,17 +164,21 @@ impl Router {
     }
 
     pub async fn resolve(&self, identifier: Option<&str>) -> Arc<str> {
+        self.resolve_or(identifier, &self.default_destination).await
+    }
+
+    pub async fn resolve_or(&self, identifier: Option<&str>, default: &Arc<str>) -> Arc<str> {
         let key: Cow<'_, str> = match identifier {
             Some(id) => match self.normalize {
                 Normalize::None => Cow::Borrowed(id),
                 Normalize::Lowercase => Cow::Owned(id.to_lowercase()),
             },
-            None => return self.default_destination.clone(),
+            None => return default.clone(),
         };
 
         if let Some(hit) = self.cache.get(key.as_ref()).await {
             self.stats.hits.fetch_add(1, Ordering::Relaxed);
-            return hit.dest(&self.default_destination);
+            return hit.dest(default);
         }
         self.stats.misses.fetch_add(1, Ordering::Relaxed);
 
@@ -215,7 +219,7 @@ impl Router {
             .try_get_with(key.into_boxed_str(), init)
             .await
             .unwrap_or(Route::Transient);
-        route.dest(&self.default_destination)
+        route.dest(default)
     }
 
     pub fn normalize(&self, identifier: &str) -> String {

src/sasl.rs

@@ -4,6 +4,10 @@
  * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-SEL
  */
 
+use encodify::base64::{self, Base64};
+
+pub const SASL_RESPONSE: Base64 = base64::LENIENT;
+
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub enum Credential {
     Plain {
@@ -98,10 +102,6 @@ pub fn extract_oauth_bearer(bytes: &[u8]) -> Option<(String, Option<String>)> {
     None
 }
 
-pub fn decode_sasl_ir(b64: &[u8]) -> Option<Vec<u8>> {
-    mail_parser::decoders::base64::base64_decode(b64)
-}
-
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -154,7 +154,7 @@ mod tests {
 
     #[test]
     fn lenient_ir_decode() {
-        let out = decode_sasl_ir(b"dGVzdAB0ZXN0AHRlc3Q=").unwrap();
+        let out = SASL_RESPONSE.decode(b"dGVzdAB0ZXN0AHRlc3Q=").unwrap();
         assert_eq!(out, b"test\0test\0test");
     }
 
@@ -204,13 +204,13 @@ mod tests {
 
     #[test]
     fn lenient_ir_tolerates_whitespace() {
-        let with_ws = decode_sasl_ir(b"dGVz dAB0\nZXN0AHRlc3Q=").unwrap();
+        let with_ws = SASL_RESPONSE.decode(b"dGVz dAB0\nZXN0AHRlc3Q=").unwrap();
         assert_eq!(with_ws, b"test\0test\0test");
     }
 
     #[test]
     fn lenient_ir_decodes_full_quads_without_padding() {
-        let out = decode_sasl_ir(b"AHRlc3QAc2VjcmV0").unwrap();
+        let out = SASL_RESPONSE.decode(b"AHRlc3QAc2VjcmV0").unwrap();
         assert_eq!(out, b"\0test\0secret");
     }
 }

src/tests/admin.rs

@@ -324,6 +324,14 @@ async fn admin_delay_holds_new_login() {
     )
     .await;
     assert_eq!(status, 400);
+    let (status, _) = admin_request(
+        admin_addr,
+        "POST",
+        "/connections/delay?identifier=user@example.com&seconds=18446744073709551615",
+        Some(TOKEN),
+    )
+    .await;
+    assert_eq!(status, 400);
 
     let listener = ctx.config.listener["pop3"].clone();
     let (mut client, server) = tcp_pair().await;
@@ -645,3 +653,164 @@ async fn admin_config_reload_rejects_invalid() {
         "legacy"
     );
 }
+
+fn switch_config(old_port: u16, new_port: u16, mapping_path: &str) -> String {
+    format!(
+        r#"
+[mapping]
+source = "file"
+normalize = "lowercase"
+[mapping.file]
+path = "{mapping_path}"
+
+[capabilities.pop3]
+allow_plain_auth_without_tls = true
+
+[routing]
+default_destination = "legacy"
+
+[destination.legacy]
+host = "127.0.0.1"
+forwarding = "none"
+allow_plaintext_auth = true
+[destination.legacy.protocol.pop3]
+port = {old_port}
+tls = "plain"
+
+[destination.next]
+host = "127.0.0.1"
+forwarding = "none"
+allow_plaintext_auth = true
+[destination.next.protocol.pop3]
+port = {new_port}
+tls = "plain"
+
+[listener.pop3]
+protocol = "pop3"
+bind = ["127.0.0.1:0"]
+tls = "plain"
+
+[admin]
+bind = "127.0.0.1:0"
+tls = "implicit"
+bearer_token = "{TOKEN}"
+min_token_len = 32
+lockout_threshold = 100
+lockout_duration = "5m"
+"#
+    )
+}
+
+async fn pop3_named_backend(name: &'static str) -> (u16, tokio::task::JoinHandle<()>) {
+    use tokio::io::{AsyncReadExt, AsyncWriteExt};
+
+    dummy_backend(move |mut sock| async move {
+        sock.write_all(b"+OK ready\r\n").await.unwrap();
+        let mut buf = Vec::new();
+        let mut scratch = [0u8; 1024];
+        while find(&buf, b"AUTH PLAIN").is_none() || find(&buf, b"\r\n").is_none() {
+            let n = sock.read(&mut scratch).await.unwrap();
+            if n == 0 {
+                return;
+            }
+            buf.extend_from_slice(&scratch[..n]);
+        }
+        sock.write_all(format!("+OK logged in at {name}\r\n").as_bytes())
+            .await
+            .unwrap();
+        let _ = sock.read(&mut scratch).await;
+    })
+    .await
+}
+
+async fn held_login_follows_mapping_change(method: &str, path: &str, mapping_update: Option<&str>) {
+    use tokio::io::AsyncReadExt;
+
+    let (old_port, old_backend) = pop3_named_backend("legacy").await;
+    let (new_port, new_backend) = pop3_named_backend("next").await;
+    let mapping = mapping_file("user@example.com\tlegacy\n");
+    let toml = switch_config(old_port, new_port, &mapping.path().display().to_string());
+    let ctx = make_ctx(&toml).await;
+
+    let admin_listener = TcpListener::bind(unused_addr()).await.unwrap();
+    let admin_addr = admin_listener.local_addr().unwrap();
+    let admin_ctx = ctx.clone();
+    let admin_config = ctx.config.clone();
+    tokio::spawn(async move {
+        let shared = std::sync::Arc::new(arc_swap::ArcSwap::new(admin_ctx));
+        let _ = crate::admin::serve(shared, admin_config, None, admin_listener).await;
+    });
+
+    let (status, _) = admin_request(
+        admin_addr,
+        "POST",
+        "/connections/delay?identifier=user@example.com&seconds=60",
+        Some(TOKEN),
+    )
+    .await;
+    assert_eq!(status, 200);
+
+    let listener = ctx.config.listener["pop3"].clone();
+    let (mut client, server) = tcp_pair().await;
+    let ctx2 = ctx.clone();
+    let handler = tokio::spawn(async move {
+        let _ = crate::proto::pop3::handle(
+            &ctx2,
+            &listener,
+            Box::new(server),
+            "203.0.113.9:40000".parse().unwrap(),
+            "127.0.0.1:110".parse().unwrap(),
+        )
+        .await;
+    });
+
+    let greeting = read_line(&mut client).await;
+    assert!(greeting.starts_with("+OK"), "greeting: {greeting}");
+    send(&mut client, b"USER user@example.com\r\nPASS secret\r\n").await;
+    tokio::time::sleep(std::time::Duration::from_millis(300)).await;
+
+    if let Some(contents) = mapping_update {
+        std::fs::write(mapping.path(), contents).unwrap();
+    }
+    let (status, _) = admin_request(admin_addr, method, path, Some(TOKEN)).await;
+    assert_eq!(status, 200);
+
+    let mut seen = Vec::new();
+    let mut scratch = [0u8; 1024];
+    while find(&seen, b"+OK logged in at").is_none() {
+        let n = tokio::time::timeout(std::time::Duration::from_secs(5), client.read(&mut scratch))
+            .await
+            .expect("held login was not released by the mapping change")
+            .unwrap();
+        assert!(n > 0, "client closed before login");
+        seen.extend_from_slice(&scratch[..n]);
+    }
+    assert!(
+        find(&seen, b"+OK logged in at next").is_some(),
+        "held login must reach the new destination, got {:?}",
+        String::from_utf8_lossy(&seen)
+    );
+
+    drop(client);
+    let _ = new_backend.await;
+    old_backend.abort();
+    let _ = handler.await;
+}
+
+#[tokio::test]
+async fn admin_mapping_put_releases_held_login_to_new_destination() {
+    // a login held by /connections/delay goes to the destination set by PUT /mappings at once
+    held_login_follows_mapping_change(
+        "PUT",
+        "/mappings?identifier=user@example.com&destination=next",
+        None,
+    )
+    .await;
+}
+
+#[tokio::test]
+async fn admin_mappings_reload_releases_held_login_to_new_destination() {
+    // a login held by /connections/delay goes to the destination loaded by /mappings/reload at once
+    held_login_follows_mapping_change("POST", "/mappings/reload", Some("user@example.com\tnext\n"))
+        .await;
+}

src/tests/config_validation.rs

@@ -501,3 +501,79 @@ sasl = ["NTLM"]
         );
     }
 }
+
+fn http_fallback_config(mapping_path: &str, fallback: &str) -> String {
+    format!(
+        r#"
+{}
+[routing]
+default_destination = "legacy"
+
+[destination.legacy]
+host = "127.0.0.1"
+proxy_protocol = false
+allow_plaintext_auth = true
+[destination.legacy.protocol.http]
+port = 80
+tls = "plain"
+
+[destination.imaponly]
+host = "127.0.0.1"
+proxy_protocol = false
+allow_plaintext_auth = true
+[destination.imaponly.protocol.imap]
+port = 143
+tls = "plain"
+
+[[http.route]]
+match = "/**"
+extract = {{ from = "authorization" }}
+fallback = "{fallback}"
+"#,
+        mapping_block(mapping_path)
+    )
+}
+
+#[test]
+fn http_route_fallback_must_name_known_http_destination() {
+    let m = mapping_file("");
+    let path = m.path().display().to_string();
+    assert!(Config::parse_and_validate(&http_fallback_config(&path, "legacy")).is_ok());
+    assert!(Config::parse_and_validate(&http_fallback_config(&path, "ghost")).is_err());
+    assert!(Config::parse_and_validate(&http_fallback_config(&path, "imaponly")).is_err());
+}
+
+fn install_script_config() -> &'static str {
+    let script = include_str!("../../install.sh");
+    let (_, rest) = script
+        .split_once("write_config_file() {\n    cat > \"$1\" <<'EOF'\n")
+        .expect("install.sh config heredoc start");
+    let (config, _) = rest
+        .split_once("\nEOF\n")
+        .expect("install.sh config heredoc end");
+    config
+}
+
+#[test]
+fn shipped_configs_validate() {
+    // every configuration shipped with the proxy passes boot validation
+    for (name, raw) in [
+        (
+            "config.sample.toml",
+            include_str!("../../resources/config.sample.toml"),
+        ),
+        (
+            "config.stalwart-upgrade.toml",
+            include_str!("../../resources/config.stalwart-upgrade.toml"),
+        ),
+        (
+            "config.dovecot-postfix.toml",
+            include_str!("../../resources/config.dovecot-postfix.toml"),
+        ),
+        ("install.sh", install_script_config()),
+    ] {
+        if let Err(e) = Config::parse_and_validate(raw) {
+            panic!("{name} fails validation: {e}");
+        }
+    }
+}

src/tests/containers/clients.rs

@@ -4,8 +4,7 @@
  * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-SEL
  */
 
-use base64::Engine;
-use base64::engine::general_purpose::STANDARD as B64;
+use encodify::base64::STANDARD as B64;
 use tokio::io::{AsyncRead, AsyncReadExt, AsyncWrite, AsyncWriteExt};
 use tokio::net::TcpStream;
 

src/tests/containers/http.rs

@@ -6,6 +6,7 @@
 
 use std::sync::Arc;
 
+use encodify::base64::STANDARD as B64;
 use tokio::io::{AsyncRead, AsyncReadExt, AsyncWrite, AsyncWriteExt};
 use tokio::net::TcpStream;
 
@@ -34,11 +35,9 @@ impl Response {
 }
 
 pub fn basic_auth(user: &str, pass: &str) -> String {
-    use base64::Engine;
-    format!(
-        "Basic {}",
-        base64::engine::general_purpose::STANDARD.encode(format!("{user}:{pass}"))
-    )
+    let mut header = String::from("Basic ");
+    B64.encode_append(format!("{user}:{pass}"), &mut header);
+    header
 }
 
 pub async fn upgrade(

src/tests/containers/jmap.rs

@@ -55,7 +55,7 @@ tls = "implicit"
 [[http.route]]
 match = "/**"
 extract = {{ from = "authorization" }}
-fallback = "default"
+fallback = "new"
 
 [listener.http]
 protocol = "http"

src/tests/containers/master_user_and_load.rs

@@ -4,8 +4,7 @@
  * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-SEL
  */
 
-use base64::Engine;
-use base64::engine::general_purpose::STANDARD as B64;
+use encodify::base64::STANDARD as B64;
 use tokio::io::{AsyncReadExt, AsyncWriteExt};
 use tokio::net::TcpStream;
 

src/tests/containers/oauth.rs

@@ -4,8 +4,7 @@
  * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-SEL
  */
 
-use base64::Engine;
-use base64::engine::general_purpose::STANDARD as B64;
+use encodify::base64::STANDARD as B64;
 use tokio::io::{AsyncRead, AsyncReadExt, AsyncWriteExt};
 use tokio::net::TcpStream;
 

src/tests/containers/scenario2.rs

@@ -163,7 +163,7 @@ tls = "implicit"
 [[http.route]]
 match = "/**"
 extract = {{ from = "authorization" }}
-fallback = "default"
+fallback = "old"
 
 [listener.http]
 protocol = "http"

src/tests/containers/stalwart.rs

@@ -830,7 +830,7 @@ fn path_of(url: &str) -> String {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use base64::Engine;
+    use encodify::base64::STANDARD as B64;
     use tokio::io::{AsyncReadExt, AsyncWriteExt};
 
     async fn imaps_auth(host: &str, port: u16, login: &str, password: &str) -> String {
@@ -838,7 +838,7 @@ mod tests {
         let mut stream = crate::tests::harness::tls_connect_client(tcp).await;
         let mut buf = [0u8; 512];
         let _ = stream.read(&mut buf).await.unwrap();
-        let ir = base64::engine::general_purpose::STANDARD.encode(format!("\0{login}\0{password}"));
+        let ir = B64.encode(format!("\0{login}\0{password}"));
         stream
             .write_all(format!("a1 AUTHENTICATE PLAIN {ir}\r\n").as_bytes())
             .await

src/tests/containers/toolbox_http.rs

@@ -40,7 +40,7 @@ tls = "implicit"
 [[http.route]]
 match = "/**"
 extract = {{ from = "authorization" }}
-fallback = "default"
+fallback = "new"
 
 [listener.http]
 protocol = "http"

src/tests/forwarding.rs

@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-SEL
  */
 
-use base64::{Engine, engine::general_purpose::STANDARD as BASE64};
+use encodify::base64::STANDARD as BASE64;
 use tokio::io::{AsyncReadExt, AsyncWriteExt};
 use tokio::net::TcpStream;
 

src/tests/http_proxy.rs

@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-SEL
  */
 
-use base64::{Engine, engine::general_purpose::STANDARD as BASE64};
+use encodify::base64::STANDARD as BASE64;
 
 use super::harness::*;
 
@@ -516,6 +516,113 @@ tls = "plain"
     handler.abort();
 }
 
+#[tokio::test]
+async fn http_route_fallback_destination_used_without_mapping() {
+    async fn backend_default(mut sock: tokio::net::TcpStream) {
+        read_req_head(&mut sock).await;
+        sock.write_all(b"HTTP/1.1 200 OK\r\nContent-Length: 7\r\nConnection: close\r\n\r\ndefault")
+            .await
+            .unwrap();
+    }
+    async fn backend_fallback(mut sock: tokio::net::TcpStream) {
+        read_req_head(&mut sock).await;
+        sock.write_all(
+            b"HTTP/1.1 200 OK\r\nContent-Length: 8\r\nConnection: close\r\n\r\nfallback",
+        )
+        .await
+        .unwrap();
+    }
+
+    let mapping = mapping_file("alice@x\tweb_default\n");
+    let mut handles = Vec::new();
+    let cases = [
+        (None, "fallback"),
+        (Some("nobody@x"), "fallback"),
+        (Some("alice@x"), "default"),
+    ];
+    for (user, expected) in cases {
+        let (port_d, bd) = dummy_backend(backend_default).await;
+        let (port_f, bf) = dummy_backend(backend_fallback).await;
+        handles.push(bd);
+        handles.push(bf);
+        let toml = format!(
+            r#"
+[mapping]
+source = "file"
+normalize = "lowercase"
+[mapping.file]
+path = "{}"
+
+[routing]
+default_destination = "web_default"
+
+[destination.web_default]
+host = "127.0.0.1"
+proxy_protocol = false
+allow_plaintext_auth = true
+[destination.web_default.protocol.http]
+port = {port_d}
+tls = "plain"
+
+[destination.web_fallback]
+host = "127.0.0.1"
+proxy_protocol = false
+allow_plaintext_auth = true
+[destination.web_fallback.protocol.http]
+port = {port_f}
+tls = "plain"
+
+[[http.route]]
+match = "/**"
+extract = {{ from = "authorization" }}
+fallback = "web_fallback"
+
+[listener.http]
+protocol = "http"
+bind = ["127.0.0.1:0"]
+tls = "plain"
+"#,
+            mapping.path().display()
+        );
+        let ctx = make_ctx(&toml).await;
+        let listener = ctx.config.listener["http"].clone();
+        let (mut client, srv) = tcp_pair().await;
+        let handler = tokio::spawn(async move {
+            let _ = crate::http::proxy::handle(
+                &ctx,
+                &listener,
+                Box::new(srv),
+                "127.0.0.1:40044".parse().unwrap(),
+                "127.0.0.1:80".parse().unwrap(),
+            )
+            .await;
+        });
+        let auth = user
+            .map(|u| {
+                format!(
+                    "Authorization: Basic {}\r\n",
+                    BASE64.encode(format!("{u}:pw"))
+                )
+            })
+            .unwrap_or_default();
+        send(
+            &mut client,
+            format!("GET / HTTP/1.1\r\nHost: x\r\n{auth}Connection: close\r\n\r\n").as_bytes(),
+        )
+        .await;
+        let resp = read_to_eof(&mut client).await;
+        assert!(
+            resp.ends_with(expected.as_bytes()),
+            "user {user:?} should reach {expected}, got {:?}",
+            String::from_utf8_lossy(&resp)
+        );
+        handles.push(handler);
+    }
+    for h in handles {
+        h.abort();
+    }
+}
+
 async fn read_until_backend(sock: &mut tokio::net::TcpStream, needle: &[u8]) -> Vec<u8> {
     let mut buf = Vec::new();
     let mut scratch = [0u8; 1024];
@@ -1346,3 +1453,82 @@ async fn http_login_delay_holds_an_authenticated_request() {
     let _ = backend.await;
     handler.abort();
 }
+
+#[tokio::test]
+async fn http_held_login_follows_mapping_change() {
+    // an http request held by a login delay is sent to the destination mapped when the hold ends
+    async fn backend(name: &'static str) -> (u16, tokio::task::JoinHandle<()>) {
+        dummy_backend(move |mut sock| async move {
+            read_req_head(&mut sock).await;
+            let _ = sock
+                .write_all(
+                    format!(
+                        "HTTP/1.1 200 OK\r\nContent-Length: {}\r\nConnection: close\r\n\r\n{name}",
+                        name.len()
+                    )
+                    .as_bytes(),
+                )
+                .await;
+        })
+        .await
+    }
+
+    let (old_port, old_backend) = backend("legacy").await;
+    let (new_port, new_backend) = backend("next").await;
+    let mapping = mapping_file("user@example.com\tweb\n");
+    let toml = format!(
+        r#"{}
+[destination.next]
+host = "127.0.0.1"
+proxy_protocol = false
+allow_plaintext_auth = true
+[destination.next.protocol.http]
+port = {new_port}
+tls = "plain"
+"#,
+        extract_http_config("127.0.0.1", old_port, &mapping.path().display().to_string())
+    );
+    let ctx = make_ctx(&toml).await;
+    let listener = ctx.config.listener["http"].clone();
+    let identifier = ctx.router.normalize("user@example.com");
+    ctx.conns.set_delay(
+        &identifier,
+        std::time::Instant::now() + std::time::Duration::from_secs(60),
+    );
+
+    let (mut client, srv) = tcp_pair().await;
+    let ctx2 = ctx.clone();
+    let handler = tokio::spawn(async move {
+        let _ = crate::http::proxy::handle(
+            &ctx2,
+            &listener,
+            Box::new(srv),
+            "127.0.0.1:40076".parse().unwrap(),
+            "127.0.0.1:80".parse().unwrap(),
+        )
+        .await;
+    });
+
+    let creds = BASE64.encode("user@example.com:pw");
+    send(
+        &mut client,
+        format!("GET /jmap HTTP/1.1\r\nHost: x\r\nAuthorization: Basic {creds}\r\nConnection: close\r\n\r\n").as_bytes(),
+    )
+    .await;
+    tokio::time::sleep(std::time::Duration::from_millis(300)).await;
+    ctx.router.upsert("user@example.com", "next").await.unwrap();
+    ctx.conns.release_delay(&identifier);
+
+    let resp = tokio::time::timeout(std::time::Duration::from_secs(5), read_to_eof(&mut client))
+        .await
+        .expect("held request was not released by the mapping change");
+    assert!(
+        find(&resp, b"\r\n\r\nnext").is_some(),
+        "held request must reach the new destination, got {:?}",
+        String::from_utf8_lossy(&resp)
+    );
+
+    let _ = new_backend.await;
+    old_backend.abort();
+    handler.abort();
+}

src/tests/imap.rs

@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-SEL
  */
 
-use base64::{Engine, engine::general_purpose::STANDARD as BASE64};
+use encodify::base64::STANDARD as BASE64;
 use tokio::io::{AsyncReadExt, AsyncWriteExt};
 
 use super::harness::*;

src/tests/managesieve.rs

@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-SEL
  */
 
-use base64::{Engine, engine::general_purpose::STANDARD as BASE64};
+use encodify::base64::STANDARD as BASE64;
 use tokio::io::{AsyncReadExt, AsyncWriteExt};
 
 use super::harness::*;

src/tests/pop3.rs

@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-SEL
  */
 
-use base64::{Engine, engine::general_purpose::STANDARD as BASE64};
+use encodify::base64::STANDARD as BASE64;
 use tokio::io::{AsyncReadExt, AsyncWriteExt};
 
 use super::harness::*;

src/tests/routing.rs

@@ -63,6 +63,29 @@ async fn router_resolves_normalizes_and_caches() {
     assert_eq!(&*router.resolve(Some("user@example.com")).await, "primary");
 }
 
+#[tokio::test]
+async fn router_resolve_or_uses_given_fallback() {
+    let mapping = mapping_file("user@example.com\tprimary\n");
+    let toml = config(&mapping.path().display().to_string());
+    let router = build_router(&toml).await;
+    let fallback: std::sync::Arc<str> = "primary".into();
+    let legacy: std::sync::Arc<str> = "legacy".into();
+
+    assert_eq!(&*router.resolve_or(None, &fallback).await, "primary");
+    assert_eq!(
+        &*router.resolve_or(Some("nobody@x"), &fallback).await,
+        "primary"
+    );
+    assert_eq!(
+        &*router.resolve_or(Some("nobody@x"), &legacy).await,
+        "legacy"
+    );
+    assert_eq!(
+        &*router.resolve_or(Some("user@example.com"), &legacy).await,
+        "primary"
+    );
+}
+
 #[tokio::test]
 async fn router_cache_hits_and_misses() {
     let mapping = mapping_file("user@example.com\tprimary\n");

src/tests/smtp.rs

@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-SEL
  */
 
-use base64::{Engine, engine::general_purpose::STANDARD as BASE64};
+use encodify::base64::STANDARD as BASE64;
 use tokio::io::{AsyncReadExt, AsyncWriteExt};
 
 use super::harness::*;

src/token.rs

@@ -4,17 +4,14 @@
  * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-SEL
  */
 
-use base64::{Engine, engine::general_purpose::URL_SAFE_NO_PAD};
+use encodify::base64::URL_SAFE_NO_PAD;
 
 use crate::sasl::Credential;
 
 pub fn bearer_identifier(token: &str, jwt_username_claim: &str) -> Option<String> {
     if let Some(rest) = token.strip_prefix("sw1.") {
         return match rest.split_once('.') {
-            Some((_body, footer)) => {
-                let decoded = URL_SAFE_NO_PAD.decode(footer).ok()?;
-                String::from_utf8(decoded).ok()
-            }
+            Some((_body, footer)) => URL_SAFE_NO_PAD.decode_to_string(footer).ok(),
             None => None,
         };
     }
@@ -61,7 +58,6 @@ pub fn identifier_from_credential(cred: &Credential, jwt_username_claim: &str) -
 #[cfg(test)]
 mod tests {
     use super::*;
-    use base64::{Engine, engine::general_purpose::URL_SAFE_NO_PAD};
 
     #[test]
     fn sw1_footer() {