warmbly/warmbly: The largest open-source B2B cold outreach and email warmup service.

The open-source agentic cold email and warmup platform.

Features · How it works · Quick start · Self-hosting · Docs · Community · Support

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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

Open http://localhost:5173 and log in with [email protected] / password123; the login code lands in Mailpit at http://localhost:18025. Every make target, the native services, and how seeding works are in the local development guide.

[!WARNING]

make dev and make up share one database, and seeded fixture accounts claim

the instance. Planning to self-host from the same machine? Read

first run first.

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:

curl -fsSL https://warmbly.com/install.sh | sh

That pulls the published release images, writes a real .env, starts the stack and prints the one-time link that claims the instance and makes you its admin. No clone, no compiler, under two minutes. Add --wizard and it asks where each store lives, what is kept and for how long, and how it is backed up. The script is checksummed at install.sh.sha256 if you would rather download, verify and read it first, --dry-run prints every file it would write without touching anything, and --demo walks the whole wizard while installing nothing. Full flag list: install.

To build it from source instead:

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

Either way you need Docker with Compose v2; the build path also wants about 10 GB of free disk. If anything looks wrong, make doctor prints the instance state and every failing check.

From here the self-hosting guide covers the rest: your own secrets, production hardening, mail and single sign-on, HTTPS, connecting Gmail and Microsoft mailboxes, scaling workers, and backups. Account recovery and every operator command live in warmblyctl, the CLI baked into the backend image; it talks to the database directly, so it works when signing in does not.

Documentation

The full docs live at docs.warmbly.com.

| Read this | To learn | |-----------|----------| | Install | The one-command install and its wizard: where the data lives, what is kept, how it is backed up | | Self-hosting guide | Building from source, then production, backups, and scaling the worker fleet | | Data control | Every store's location, every retention window, instance backups, and moving to another host | | 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 | | warmblyctl | The operator CLI: creating accounts, setting passwords, granting admin, and instance status | | 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 [email protected]

Support and enterprise

[!NOTE]

Need a hand? We are happy to help. Ask in Discord, open a GitHub issue, or email [email protected], 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 [email protected] 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 [email protected] instead of opening a public issue. We prefer responsible disclosure and credit reporters in the release notes.

License

Apache License 2.0. Copyright 2026 Mindroot Ltd. See LICENSE.