macOS Sonoma introduces MailKit API, dropping support for legacy mail Plug-ins

Apple's latest operating system, macOS Sonoma, comes packed with new features designed to enhance user experience. Among the notable additions are Game Mode, interactive desktop widgets, and improved PDF viewing and editing capabilities. However, macOS Sonoma brings significant changes that may affect users relying on legacy Apple Mail app plug-ins. Apple has confirmed the discontinuation of support for these plug-ins, which has repercussions for certain third-party apps.

One app directly affected by this change is AltStore, which relies on a Mail app plug-in for its functionality. Developers at AltStore have acknowledged that macOS Sonoma will no longer support legacy Mail plug-ins, prompting them to work on a new authentication method to overcome the incompatibility. This underscores the need for users with apps dependent on legacy Mail plug-ins to exercise caution before upgrading to macOS Sonoma, as compatibility issues may arise. To address the evolving landscape of Mail extensions, Apple has introduced the MailKit API as a replacement for legacy plug-ins in macOS Monterey. The MailKit API offers a more restricted framework, but it enhances security by providing additional layers of protection for user data. This shift to the MailKit API signifies Apple's commitment to maintaining a secure and unified ecosystem. Going forward, the MailKit API will be the sole method for creating extensions for the Mail app, ensuring a standardized and secure approach for developers and users alike.

Users with apps dependent on legacy plug-ins should wait for updates from developers to ensure compatibility with macOS Sonoma while benefiting from the enhanced security and functionality of the MailKit API.