warmbly

Warmbly is a cold outreach platform you run yourself: your sending IPs, your Postgres, your servers, nothing tied to a vendor's database. Connect your mailboxes, write sequenced campaigns, and it sends the mail, tracks the replies, and keeps your sender reputation healthy.

https://github.com/user-attachments/assets/378a510a-bb99-425f-925e-04300184938b

Everything a sending team needs sits in one dashboard, collaborative in real time so teammates see each other's presence and edits with no refresh:

Campaigns send multi-step sequences with per-mailbox daily caps and spacing.
The unified inbox pulls every connected mailbox and its replies into one view.
A built-in CRM tracks contacts, pipelines, deals, tasks, and meetings.
Deliverability surfaces bounces, complaints, suppression, and inbox placement.
Automations run branching reply playbooks on a visual canvas, with AI steps that read a reply and act on it.
Integrations sync the CRM and automations out to HubSpot, Slack, and more.
Warmup builds real sender reputation through a pool of monitored mailboxes.

The same code runs on a single VPS or across a fleet of cheap servers, so you add capacity by adding machines.

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Connect your mailboxes

Connect Gmail and Google Workspace with one-click OAuth, Microsoft 365 over its own OAuth, or any other provider (Zoho, Fastmail, a self-hosted server) over SMTP + IMAP. Each mailbox warms, sends, and syncs on its own, with its own daily cap and spacing, and credentials sealed with per-organization envelope encryption. See Mailboxes.

Integrations

Automations and the built-in CRM connect out to the tools you already run: ping Slack on a positive reply, push a won deal to your CRM, or book meetings straight from replies.

Category	Providers
CRM	HubSpot, Salesforce, Pipedrive, Close
Automation	Zapier, Make, n8n
Notifications	Slack, Discord
Meetings	Calendly, Cal.com
Data	Google Sheets

Everything is also reachable through a scoped REST API, HMAC-signed webhooks, and a realtime WebSocket. See the API reference.

Warmup

Warmup only produces real results with a pool of real mailboxes warming against each other, and Warmbly maintains that pool. Volume starts low and ramps gradually per mailbox, replies happen at a natural rate, and mailboxes that show spam patterns or forged tokens are scored and auto-blocked so the pool stays clean for everyone. See Warmup.

Quick start

You need Docker, Go 1.25, and pnpm.

git clone https://github.com/warmbly/warmbly && cd warmbly
make dev

One command brings up the backing services in Docker, applies migrations, seeds demo data, and starts the backend, worker, and dashboard natively. Open http://localhost:5173 and log in with dev@warmbly.com / password123. Full setup, seeding, and troubleshooting live in the local development guide.

How it works

Warmbly splits into a control plane (backend API, consumer, Postgres, Redis, and the event bus) that owns every piece of state, and an execution plane of interchangeable Go workers that send and sync mail. Workers never connect to Postgres, and outbound mail leaves through each mailbox's own provider (Gmail API, Microsoft Graph, or SMTP relay), not the worker's IP, so you add throughput by running more workers. Secrets use envelope encryption, with a local AES master key by default or AWS KMS if you prefer. Full write-up in the architecture docs.

Self-hosting

Warmbly runs with no cloud account of any kind: no AWS, no GCP, no Stripe, no Kafka. One command brings up the whole platform on local, open-source pieces:

git clone https://github.com/warmbly/warmbly && cd warmbly
make up               # or: docker compose up --build

Dashboard on :5173, admin on :5174, API on :8080. Every external dependency is picked by an environment variable, so you swap in a cloud service only if you want one:

Concern	Self-host default	Optional / cloud
Database	PostgreSQL 16	RDS / Cloud SQL, any Postgres
Cache	Redis (or Valkey)	ElastiCache
Event bus	NATS JetStream (~15 MB, one binary)	Kafka (`-tags kafka`)
Blob storage	Filesystem	S3, MinIO, R2, B2
KMS / root key	Local AES master key	AWS KMS
Task scheduler	In-process Postgres poller	GCP Cloud Tasks
Codec	JSON	Avro + Schema Registry
Captcha	Off	Cloudflare Turnstile
Payments	Off (everything unlocked)	Stripe

Scaling is by mailboxes and workers, not IPs: add throughput by connecting more mailboxes and running more workers. Reaching it from another machine, connecting Gmail mailboxes, the secrets you must set, and day-2 operations are all in the deployment guide.

Tech stack

Component	Tech
Backend API	Go 1.25 + Gin
Consumer	Go (event-bus driven)
Worker	Go (Kafka / NATS subscriber)
Tracking	Rust + Axum
Realtime	Elixir + Phoenix Channels
Dashboard	React 19 + Vite + Tailwind v4
Admin UI	React 19 + Vite + Tailwind v4
Database	PostgreSQL 16
Cache	Redis 7 (or Valkey / KeyDB)
Event bus	NATS JetStream (default) or Kafka

Documentation

The full docs live at docs.warmbly.com: product guides, the API reference, and the engineering docs. Start here:

Read this	To learn
Local development	Every make target, the native services, and how seeding works
Sandbox	One command spins up a full demo org that sends, replies, opens, clicks, and warms itself
Architecture	How the control plane and the workers split the job, plus the encryption model
Deployment guide	Taking it to production and scaling the worker fleet
API reference	Endpoints, auth, permissions, and webhooks

Contributing

Pull requests are welcome. Keep each one to a single logical change, and open an issue first for larger design or product changes. Before you open a PR, run the checks for the tree you touched (make fmt and make lint for Go, pnpm typecheck and pnpm lint for the frontends). See CONTRIBUTING.md.

Security

Found a vulnerability? Email team@warmbly.com instead of opening a public issue. We prefer responsible disclosure and credit reporters in the release notes.

README.md

What is Warmbly