Mail app in macOS had support for plug-in and many professional users were relying on these plug-ins to manage their incoming and outgoing mail.

Apple introduced MailKit allowing developers to build Mail extensions as a replacement for legacy plug-ins. As of now, several projects are still using plug-ins. These plug-ins will stop working with update to macOS 14 Sonoma.

Some developers already started the migration to Mail extensions.

Apple Developer: MailKit




Get familiar with MailKit, consider migration approach if applicable.

QA engineer:

Business as usual.


Consider migration to MailKit if Mail plug-ins are currently used.

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