warmbly

Warmbly runs cold email campaigns from the mailboxes you already own and warms them so they keep landing in the inbox. Opens, clicks, and replies land in a shared dashboard the moment they happen, and it's AI-native, so your team and its agents work in it together, live.

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

Features

Campaigns - multi-step sequences with per-mailbox caps and spacing
Unified inbox - every mailbox and reply in one place
CRM - contacts, pipelines, deals, tasks, meetings
Warmup - a pool of monitored mailboxes, not throwaway accounts
Deliverability - bounces, complaints, suppression, inbox placement
Automations - visual reply playbooks with AI steps
Integrations - HubSpot, Slack, Zapier, REST API, webhooks
Realtime - live presence and edits across your team

How it works

Warmbly splits into a control plane (backend API, consumer, Postgres, Redis, and the event bus) that owns all state, and an execution plane of interchangeable Go workers that send and sync mail. Workers never touch Postgres, and outbound mail leaves through each mailbox's own provider, not the worker's IP, so you add throughput by running more workers.

flowchart LR
  MB["Your mailboxes"] --> API
  subgraph CP["Control plane"]
    direction TB
    API["Backend API"] --> DB[("Postgres")]
    API --> BUS{{"Event bus"}}
  end
  BUS --> W1["Worker"]
  BUS --> W2["Worker"]
  BUS --> W3["Worker"]
  W1 --> P["Gmail · Microsoft · SMTP"]
  W2 --> P
  W3 --> P
  P --> R["Recipients"]

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.

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, then read the login code out of Mailpit at http://localhost:18025 (the native dev stack keeps the emailed code on so the flow stays exercised; a self-hosted install does not). Full setup lives in the local development guide.

Warning

make dev and make up share one Docker Compose project, one volume, and one warmbly_dev database, and make dev seeds fixture accounts by default. Those accounts become your instance's accounts, which permanently retires the first-run claim link make up prints. Use make dev SEED=false on a database you intend to self-host from. See first run.

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

That is the whole install. make up waits for the backend and prints a one-time link that claims the instance and makes you its admin. Open it, pick a password, and you are in.

You need Docker with Compose v2 and about 10 GB of free disk; the first run builds the images once, which takes roughly 6 minutes.

Nothing else is required. No SMTP relay, no captcha keys, no cloud account, no .env to hand-write, and no separate command to grant yourself admin. When you are ready to change something, cp .env.example .env and edit it: the template boots as-is, and every variable in it is documented in the configuration reference. Generate your own secrets and set APP_ENV=prod before anyone else can reach the instance; the file has the commands. To skip the claim link entirely, set WARMBLY_BOOTSTRAP_EMAIL and WARMBLY_BOOTSTRAP_PASSWORD_HASH before the first start and the owner account exists when it comes up.

Three things that catch people, all covered in first run:

The link is gone. It is single use and lasts 24 hours. Print another with docker compose -p warmbly exec backend warmblyctl setup-link, or make claim.
No link was printed at all. The database already has accounts, so the instance is already claimed. Add yourself with docker compose -p warmbly exec backend warmblyctl user create --email you@example.com --admin.
make dev and make up share one database. Seeding in one claims the other. That is the usual reason there was no link.

Note

Signing in never depends on outbound mail. Under Docker Compose, platform email defaults to MAIL_TRANSPORT=log, so password resets and invitations are written to the backend logs until you point SMTP_* at a real relay. Team invitations still work without one: invite the person under Settings > Members, then copy the invite link from their row under Pending invitations and send it yourself. See accounts and access.

➡️ Follow the step-by-step self-hosting guide for the full walkthrough: setting your own secrets, verifying the stack is healthy, configuring mail and single sign-on, exposing it on your network or behind HTTPS, connecting Gmail and Microsoft mailboxes, scaling workers, backups, and a troubleshooting table for the errors people actually hit.

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	Kafka (`-tags kafka`)
Blob storage	Filesystem	S3, MinIO, R2, B2
KMS / root key	Local AES master key	AWS KMS
Payments	Off (everything unlocked)	Stripe

Scaling is by mailboxes and workers, not IPs.

Documentation

The full docs live at docs.warmbly.com.

Read this	To learn
Self-hosting guide	Step-by-step install, then production, backups, and scaling the worker fleet
First run	Claiming the instance, reissuing the setup link, and what to do when accounts already exist
Accounts and access	Registration modes, inviting people with or without a mail relay, SSO, and recovering access
Configuration reference	Every environment variable, its default, and whether changing it needs a restart
Instance health	The checks the admin panel runs against your deployment, and `make doctor`
Troubleshooting	The errors self-hosters actually hit, and the command that fixes each one
Local development	Every make target, the native services, and how seeding works
Architecture	How the control plane and workers split the job, plus the encryption model
API reference	Endpoints, auth, permissions, and webhooks

Community

Have a question, found a bug, or want to shape where Warmbly goes next?

Discord - chat with the team and other senders
GitHub Issues - report bugs and request features
X / @WarmblyHQ - follow along for updates and releases
Email - reach us at team@warmbly.com

Support and enterprise

Note

Need a hand? We are happy to help. Ask in Discord, open a GitHub issue, or email team@warmbly.com, and someone on the team will get back to you.

Running Warmbly at scale, or would you rather we run it for you? We offer enterprise support and managed infrastructure: we can host and operate the whole platform for your organization, help you deploy and scale the worker fleet, tune deliverability, migrate your sending onto Warmbly, and stand behind it with a support agreement built around your team. Tell us what you need at team@warmbly.com or reach out on X.

Star the repository ⭐

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.

License

Languages

Go 41.1%

TypeScript 36.6%

Swift 10%

Astro 9.4%

Elixir 0.9%

Other 1.9%