Stalwart Mail Server — #3 Alternative to Gmail / Outlook
All-in-one memory-safe Rust mail and collaboration server speaking JMAP, IMAP4, and SMTP
Stalwart replaces sprawling Postfix + Dovecot + Rspamd stacks with a single Rust binary featuring JMAP, IMAP4, SMTP, CalDAV/CardDAV, DMARC/DKIM/ARC, Sieve scripting, and encryption at rest.
License: AGPL-3.0 · Pricing: Open Core · Compare all Gmail / Outlook alternatives · Official Website