macOS Sonoma Drops Support for Legacy Mail App Plug-ins - MacRumors
Skip to Content

macOS Sonoma Drops Support for Legacy Mail App Plug-ins

by

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!)

Tag: Apple Mail
Related Forum: macOS Sonoma

Popular Stories

iCloud iPhone 17 Pro

iPhone Users Who Pay for iCloud Storage Get Two New Perks on iOS 27

Tuesday June 9, 2026 11:29 am PDT by
If you pay for extra iCloud storage on your iPhone, beyond the 5GB included for free, you might receive two more perks on iOS 27 at no additional cost. First, Apple said there will be daily usage limits for some of the new and enhanced Apple Intelligence features on iOS 27, including image generation. However, the company noted that "increased access" is available with "most" iCloud+ storage ...
Read Full Article
WWDC26 MR Live Coverage Article

WWDC 2026 Apple Event Live Keynote Coverage: iOS 27, Revamped Siri, and More

Monday June 8, 2026 9:15 am PDT by
Apple's Worldwide Developers Conference (WWDC) starts today with the traditional keynote kicking things off at 10:00 a.m. Pacific Time. MacRumors is on hand for the event and we'll be sharing details and our thoughts throughout the day. We're expecting to see a number of software-related announcements today, headlined by a reset on Apple's push into AI that should see a significant overhaul...
Read Full Article • 1084 comments
macOS Golden Gate Mac

Apple Announces macOS 27 Golden Gate With New Siri and 'Tons' of Refinements

Monday June 8, 2026 10:19 am PDT by
Apple today announced that macOS 27 is named macOS Golden Gate. Much like Mac OS X Snow Leopard in 2009, Apple said it focused on improving macOS's performance and dozens of underlying technologies this year. Apple says macOS Golden Gate offers quicker AirDrop transfers, faster network file browsing, improved syncing in the Messages app, better Spotlight search suggestions, and other...
Read Full Article • 129 comments

Top Rated Comments

Max Webb Avatar
Max Webb
39 months ago
I didnt even know mail had plugin support full stop.
Score: 29 Votes (Like | Disagree)
redheeler Avatar
redheeler
39 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
erikkfi
39 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)
D
ddauerbach
39 months ago
I'm really going to miss the really really useful SmallCubed Mailsuite suite of plugins.
Score: 11 Votes (Like | Disagree)
B
BarryTheWebdork
39 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
zorinlynx
39 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)
Read All Comments