mailcow

mailcow is an open-source Docker-based groupware and email suite built from established components including Postfix, Dovecot, Rspamd, SOGo, Redis, MariaDB, Nginx, and Unbound. Its main advantage is a modern admin UI around a full mail-server stack.

An agent stack treats email as a two-way primitive. Inbound has to arrive as structured JSON a tool call can consume, sends have to be safe to retry when a model loop repeats itself, and every action needs an audit trail. A provider without inbound parsing only solves half the problem.

Against inbound parsing into tool calls and model-generated sends that must not duplicate, mailcow covers inbound parsing, event stream, and multi-tenant support, and does not cover idempotency keys, webhook coverage, batch sending, and SDK breadth. Whether that gap matters depends on how central those are to the build.

• Inbound parsing: Yes
• Idempotency keys: No
• Webhooks: No
• Operating since: Not published
• Event stream: Yes
• Best published rate per 1,000: Tiers not published in comparable form
• Batch sending: No
• SDKs: None
• Multi-tenant: Yes

Self-hosted deliverability depends on DNS, IP history, spam controls, and operator discipline. mailcow bundles Rspamd, DKIM support, quarantine controls, and administration UI around the stack.

Teams that want to self-host a full email and groupware suite.

Small product teams trying to avoid mail-server operations.