Running an actual inbox under your own domain — receiving, sending, and spam-filtering mail without routing it through a third party's servers.
| App | License | FOSS problems | SSO | Users | Tested |
|---|---|---|---|---|---|
| mailcowDockerized, full self-hosted mail server stack — Postfix, Dovecot, SOGo webmail/groupware, Rspamd, and ClamAV wired together behind one admin UI. | GPLv3 | — | ✅ | Unlimited | ❌ |
| StalwartAll-in-one mail server written in Rust — SMTP, IMAP, JMAP, POP3, and CalDAV/CardDAV/WebDAV in a single binary, with an open-core Enterprise tier on top. | AGPL-3.0 (core) / Stalwart Enterprise License (add-ons) | Multi-tenancy, the fuller admin dashboard, and AI-assisted features are Enterprise-License-only, not AGPL | ✅ | Unlimited (mailbox-count limited under an Enterprise license) | ❌ |