From d2f9f1a1a47fbdca013ec6c2612982f1fb8b376e Mon Sep 17 00:00:00 2001
From: Linus Rath <139418639+rathlinus@users.noreply.github.com>
Date: Sat, 31 Oct 2026 01:09:49 +0100
Subject: [PATCH] fix: send from a shared mailbox through its own identity for
 the from address #1450

---
 lib/__tests__/jmap-send-group-account.test.ts | 40 ++++++++++++++++++-
 lib/jmap/client.ts                            | 17 +++++++-
 2 files changed, 54 insertions(+), 3 deletions(-)

diff --git a/lib/__tests__/jmap-send-group-account.test.ts b/lib/__tests__/jmap-send-group-account.test.ts
index a6b9cb2ed..7bd9648ae 100644
--- a/lib/__tests__/jmap-send-group-account.test.ts
+++ b/lib/__tests__/jmap-send-group-account.test.ts
@@ -48,7 +48,7 @@ interface Recorded {
   identityId?: string;
 }
 
-function mockServer(): Recorded {
+function mockServer(identities = IDENTITIES): Recorded {
   const rec: Recorded = {};
   vi.spyOn(globalThis, 'fetch').mockImplementation(async (_url, init) => {
     const { methodCalls } = JSON.parse((init as { body: string }).body) as { methodCalls: MethodCall[] };
@@ -60,7 +60,7 @@ function mockServer(): Recorded {
           { id: `${accountId}-sent`, name: 'Sent', role: 'sent' },
         ] }, callId];
       }
-      if (name === 'Identity/get') return [name, { list: IDENTITIES[accountId] ?? [] }, callId];
+      if (name === 'Identity/get') return [name, { list: identities[accountId] ?? [] }, callId];
       if (name === 'Email/set') {
         if (args.create) {
           rec.emailSetAccount = accountId;
@@ -154,6 +154,42 @@ describe('JMAPClient.sendEmail picks the account that owns the From identity (#1
     expectAccount(rec, 'grp');
   });
 
+  // #1450: the composer's identity ids are the member's own. In the group
+  // account the same id can be another of the group's addresses, and the
+  // server takes MAIL FROM from the identity the submission names.
+  describe('identity ids of the member’s account (#1450)', () => {
+    const COLLIDING: Record<string, Array<{ id: string; email: string }>> = {
+      me: [
+        { id: 'by', email: 'info@radar.example' },
+        { id: 'bw', email: '*@lists.example' },
+        { id: 'c', email: 'carol@example.org' },
+      ],
+      grp: [
+        { id: 'by', email: 'info@alias.example' },
+        { id: 'bw', email: 'info@alias.example' },
+        { id: 'b7', email: 'info@radar.example' },
+        { id: 'w', email: '*@lists.example' },
+      ],
+    };
+
+    it.each([
+      ['the From address', 'info@radar.example', 'by', 'b7'],
+      ['a sub-addressed From', 'info+news@radar.example', 'by', 'b7'],
+      ['a From covered by a wildcard identity', 'announce@lists.example', 'bw', 'w'],
+    ])('submits through the group’s identity for %s', async (_case, fromEmail, memberId, groupId) => {
+      const rec = mockServer(COLLIDING);
+      await send(createClient({ me: 'carol@example.org', grp: 'team' }), fromEmail, memberId);
+      expectAccount(rec, 'grp');
+      expect(rec.identityId).toBe(groupId);
+    });
+
+    it('keeps the id when it names the From address in the group account too', async () => {
+      const rec = mockServer();
+      await send(createClient({ me: 'carol@example.org', grp: 'team' }), 'team@example.org', 'b');
+      expect(rec.identityId).toBe('b');
+    });
+  });
+
   describe('drafts', () => {
     const draft = (client: JMAPClient, fromEmail: string, draftId?: string, options?: { accountId?: string; previousDraftAccountId?: string }) =>
       client.createDraft(['rcpt@example.net'], 'Subject', 'body', undefined, undefined, 'b', fromEmail, draftId,
diff --git a/lib/jmap/client.ts b/lib/jmap/client.ts
index ea94d4071..02e562a71 100644
--- a/lib/jmap/client.ts
+++ b/lib/jmap/client.ts
@@ -4865,13 +4865,28 @@ export class JMAPClient implements IJMAPClient {
             ? identities.find((id) => id.email.toLowerCase() === requestedMailFrom.toLowerCase())
             : undefined;
           if (!matchingIdentity && identityId) {
-            matchingIdentity = identities.find((id) => id.id === identityId);
+            // Identity ids are per account, and the composer's come from the
+            // user's own account. In a shared account the same id can be
+            // another of its addresses, and the server derives MAIL FROM from
+            // that identity (#1450): there the id only counts when it names
+            // the From address.
+            const byId = identities.find((id) => id.id === identityId);
+            if (byId && (targetAccountId === this.accountId || !fromEmail || emailMatchesLogin(byId.email, fromEmail))) {
+              matchingIdentity = byId;
+            }
           }
           if (!matchingIdentity) {
             // Addresses compared as the server does: regardless of case.
             const target = fromEmail || this.username;
             matchingIdentity = identities.find((id) => emailMatchesLogin(id.email, target));
           }
+          if (!matchingIdentity && fromEmail) {
+            // A sub-addressed From or one covered by a wildcard identity, the
+            // other ways resolveSendAccountId picks an account.
+            const from = parseRecipientString(fromEmail).email.toLowerCase();
+            matchingIdentity = identities.find((id) => identityEmailIsSubAddressOf(id.email, from))
+              ?? identities.find((id) => identityEmailIsWildcardFor(id.email, from));
+          }
           finalIdentityId = matchingIdentity?.id || identities[0].id;
           identityReplyTo = matchingIdentity?.replyTo || identities[0].replyTo;
           identityEmail = (matchingIdentity || identities[0]).email;