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
- macOS Sonoma Drops Support for Legacy Mail App Plug-ins
- macOS Sonoma drops support for legacy Mail plug-ins; breaks support for some apps
Developer:Get familiar with MailKit, consider migration approach if applicable.
QA engineer:Business as usual.
PM/DM:Consider migration to MailKit if Mail plug-ins are currently used.