RIP Apple Mail Plug-ins

Adam Tow:

I understand Apple’s reasoning behind this decision, and I am by no means advocating for the boycott of Apple, Mail, or anything like that.

However, MailKit has not been improved enough to serve as a viable alternative for Mail Plug-In developers. WWDC 2022 and 2023 came and went without additional labs or sessions dedicated to framework enhancements. The lack of a viable solution to replace the functionality of Mail Plug-Ins in macOS Sonoma means that macOS 14 will be a disappointment for Mail users.

[…]

I’ll be updating the MsgFiler website with a notice of the impending shutdown of the app. I will take a look to see if filing messages using pure AppleScript works better today. Unfortunately, seeing that my feedbacks dating back to 2011 (FB5933458, FB5480300, FB5929173, FB6078156) have yet to be addressed, I’m not optimistic. When Sonoma comes out, I’ll pull MsgFiler from the App Store, since there’s no way to specify a maximum macOS version, only a minimum macOS version.

[…]

I am now writing this post to seek the public’s assistance in raising awareness, not only for my app, which I am bidding farewell to, but also for all the fantastic plug-ins developed by the Mail Plug-in community over the years[…]

SpamSieve is lucky in that it will be able to switch to using a Mail App Extension, with some of the plug-in’s functionality moving into the app itself and AppleScript. However, there are some limitations/bugs that I hope Apple will address before Sonoma ships, and I hope that it will expand the MailKit API in future versions to enable more features and better performance for SpamSieve and other extensions.

Some other plug-ins are also being rebuilt as extensions, albeit with reduced functionality and ease of use. For others, that will not be possible. MailSuite cannot be rebuilt as an extension, so SmallCubed is making a whole new mail client.

There’s some speculation that Apple wanted to get rid of Mail plug-ins because they were being used to sideload iOS apps. Having code running inside the Mail process made it possible to use a special entitlement that Mail had. However, it’s still possible to abuse that entitlement in Sonoma by disabling SIP. It seems like the familiar pattern of restrictions due to the App Store that hurt good faith developers without actually preventing others from bypassing security/privacy protections. Plus, iOS sideloading will be legally mandated, anyway, at least in certain countries.

On the plus side, I’m happy to be able to build on top of an official API. As Apple has expanded security protections, it made installing Mail plug-ins increasingly more difficult for users. With extensions, you can just click a checkbox in Mail’s settings. And the places to hook into Mail are now stable, rather than changing with each macOS version and with the specter of extension points disappearing as Mail was rewritten with more static Swift code. In theory, I will be able to spend more time improving the app rather than just keeping it working as Mail and macOS evolve. The downside of extensions, though, in addition to the limited functionality, is that we are dependent on Apple to fix bugs, because we can no longer patch them in Mail ourselves.

Previously:

• macOS 14 Sonoma Announced
• Sideloading Rumored for iOS 17
• Sideloading via AltStore
• Mail App Extensions

Update (2023-06-15): See also: MacRumors and 9to5Mac.

Update (2023-07-25): Houdah Software:

HoudahSpot and Tembo rely on an Apple Mail application plug-in to search mail messages. Mail on macOS 14 no longer supports plug-ins. HoudahSpot and Tembo will lose their ability to find Apple Mail message files.

The plug-in was itself a workaround for a change that Apple made to Spotlight.

Previously:

• Spotlight Excludes Mail Folder on macOS 10.15

AltStore Apple Mail AppleScript Bug E-mail E-mail Client Entitlements Extensions Mac macOS 14 Sonoma Mail App Extensions MailMaven MailTags MsgFiler Security Sideloading SpamSieve Sunset System Integrity Protection

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