macOS Sonoma Drops Support for Legacy Mail App Plug-ins

With macOS Monterey in 2021, Apple introduced a MailKit framework that developers can use to build modern and secure extensions for the Mail app on the Mac. Extensions can be created to block content, perform message actions, improve security, and more.

General macOS Mail Feature
In turn, Apple said legacy Mail app plug-ins would stop functioning in a future macOS release, and it appears that time has now come. AltStore today said it confirmed with Apple during WWDC last week that plug-ins are not supported on macOS Sonoma, and that MailKit-based extensions are the only supported solution going forward.


While MailKit extensions are more secure, they have more limited functionality compared to legacy plug-ins, so not all plug-ins may live on as extensions.

Legacy plug-ins cannot be opened in the Mail app as of the first beta version of macOS Sonoma. The update will be released to the public later this year.

(Thanks, @aaronp613!)

Related Forum: macOS Sonoma

Popular Stories

maxresdefault

Apple Shows Off a Key Reason to Upgrade to the iPhone 17

Saturday February 7, 2026 9:26 am PST by
Apple today shared an ad that shows how the upgraded Center Stage front camera on the latest iPhones improves the process of taking a group selfie. "Watch how the new front facing camera on iPhone 17 Pro takes group selfies that automatically expand and rotate as more people come into frame," says Apple. While the ad is focused on the iPhone 17 Pro and iPhone 17 Pro Max, the regular iPhone...
apple wallet drivers license feature iPhone 15 pro

Apple Says These 7 U.S. States Plan to Offer iPhone Driver's Licenses

Monday February 9, 2026 6:24 am PST by
In select U.S. states, residents can add their driver's license or state ID to the Apple Wallet app on the iPhone and Apple Watch, and then use it to display proof of identity or age at select airports and businesses, and in select apps. The feature is currently available in 13 U.S. states and Puerto Rico, and it is expected to launch in at least seven more in the future. To set up the...
m5 macbook pro deal

Why You Shouldn't Buy the Next MacBook Pro

Tuesday February 10, 2026 4:27 pm PST by
Apple is planning to launch new MacBook Pro models as soon as early March, but if you can, this is one generation you should skip because there's something much better in the works. We're waiting on 14-inch and 16-inch MacBook Pro models with M5 Pro and M5 Max chips, with few changes other than the processor upgrade. There won't be any tweaks to the design or the display, but later this...
iOS 26

Apple Releases iOS 26.3 and iPadOS 26.3

Wednesday February 11, 2026 10:07 am PST by
Apple today released iOS 26.3 and iPadOS 26.3, the latest updates to the iOS 26 and iPadOS 26 operating systems that came out in September. The new software comes almost two months after Apple released iOS 26.2 and iPadOS 26.2. The new software can be downloaded on eligible iPhones and iPads over-the-air by going to Settings > General > Software Update. According to Apple's release notes, ...
Apple Logo Zoomed

Apple Expected to Launch These 10+ Products Over the Coming Months

Tuesday February 10, 2026 6:33 am PST by
It has been a slow start to 2026 for Apple product launches, with only a new AirTag and a special Apple Watch band released so far. We are still waiting for MacBook Pro models with M5 Pro and M5 Max chips, the iPhone 17e, a lower-cost MacBook with an iPhone chip, long-rumored updates to the Apple TV and HomePod mini, and much more. Apple is expected to release/update the following products...

Top Rated Comments

Max Webb Avatar
35 months ago
I didnt even know mail had plugin support full stop.
Score: 29 Votes (Like | Disagree)
redheeler Avatar
35 months ago
Over a decade on MacOS and this is the first time I heard that the Mail app supports extensions.
Score: 26 Votes (Like | Disagree)
erikkfi Avatar
35 months ago

While MailKit extensions are more secure, they have more limited functionality compared to legacy plug-ins, so not all plug-ins may live on as extensions.
Apple loves doing this kind of thing -- see how they ruined Safari extensions -- and then they wonder why their native apps' usage stagnates rather than grows.
Score: 16 Votes (Like | Disagree)
35 months ago
I'm really going to miss the really really useful SmallCubed Mailsuite suite of plugins.
Score: 11 Votes (Like | Disagree)
35 months ago

I'm really going to miss the really really useful SmallCubed Mailsuite suite of plugins.
I registered just to upvote this. SmallCubed is apparently going to release its own mail client now. So... well done, Apple.
Score: 8 Votes (Like | Disagree)
zorinlynx Avatar
35 months ago
I still use Thunderbird because Apple Mail just isn't as capable. (Though I do use Apple Mail on my iPhone because the only mail client that was ever better on mobile was Sparrow and Google bought and killed that.)

People like to call Thunderbird "old" and "archaic" but E-mail hasn't changed much in 20 years. Thunderbird still does the job as well as it ever has, and they've recently started putting more development work into it so it will likely get even better moving forward.

Seriously, if you're a mail "power user", consider Thunderbird.
Score: 7 Votes (Like | Disagree)