macOS Sonoma abandons legacy Mail app plug-in support

Bad news for you if you are a fan of the external plugins for the legacy Mail app on your Mac. According to a recent report, Apple will abandon legacy Mail app plug-in support with macOS Sonoma.

According to  AltStore, the support for legacy Mail app plug-ins will no longer be available for developers and users. "Confirmed in WWDC labs that legacy Mail plug-ins are NOT supported on macOS Sonoma. MailKit-based extensions are the only supported method going forward," said AltStore in its tweet.

Apple debuted the MailKit framework with macOS Monterey in 2021, allowing programmers to create cutting-edge and safe additions to the Mail app on the Mac. Extensions may be developed to filter information, send messages, enhance security, and other functions.

Everyone knew that it was coming, and it is expected to be officially announced by Apple soon. However, AltStore has already obtained the information and tweeted it out to confirm the change.

PSA: Confirmed in WWDC labs that legacy Mail plug-ins are NOT supported on macOS Sonoma. MailKit-based extensions are the only supported method going forward.

AltServer's Mail plug-in will no longer work once you update, but we're working on a new method we hope to release soon.

— AltStore.io (@altstoreio) June 14, 2023

What is Mailkit framework?

According to Apple: "MailKit lets your app include an app extension that customizes several features of Mail. A Mail app extension provides one or more of the following enhancements:"

• A content blocker defines rules to prevent loading content when users view messages.
• An action handler performs actions such as flagging, setting colors, or archiving when Mail downloads messages.
• A compose session handler validates recipient email addresses, displays a view controller on Mail’s compose windows, confirms if messages are suitable for delivery, and adds custom headers.
• A message security handler secures messages using encryption and digital signatures.

Not all plug-ins may survive as extensions, even though MailKit extensions are more secure and have less functionality than older plug-ins. Since the first macOS Sonoma beta, legacy plug-ins cannot be opened in the Mail app. The public will receive the update later this year.

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