Open Source Alternatives to Apple Mail

Switching from Apple Mail to Thunderbird gets you the same standards-based IMAP/POP3/CalDAV support without being locked to macOS and iOS — Thunderbird runs on Linux and Windows too, useful for anyone who splits time across platforms or wants to leave the Apple ecosystem later without losing their mail workflow. It adds built-in OpenPGP encryption and an extension ecosystem Apple Mail doesn’t offer, though it doesn’t replicate Apple Mail’s Handoff continuity between Mac and iPhone or its default Mail Privacy Protection tracking-pixel blocking, which depends on Apple’s own infrastructure.