Poste.io

Poste.io is a full mail server solution packaged as a single Docker container. It bundles SMTP, IMAP, POP3, a webmail client (RainLoop), and an administrative interface out of the box. Setup takes minutes: pull the image, mount a volume for data, and you have a working email system with automatic Let's Encrypt certificates.

The admin panel gives you control over domains, mailboxes, aliases, and routing rules without touching config files. Greylisting, DKIM signing, SPF validation, and antivirus (ClamAV) are included. The built-in spam filter uses RBLs and content analysis. It supports MySQL or SQLite for storage, and can relay through external SMTP services. The container runs on any host with Docker, making it cloud and VPS friendly.

Poste.io is available under a freemium model: the free edition covers unlimited domains and mailboxes with core features. Paid licenses unlock advanced functions like sieve filters, push notifications, and multi-language support. The project maintains a solid reputation for simplicity. It is an especially good fit for small businesses or teams that want self-hosted email without the usual configuration headache.