macOS Monterey to Support All-New Mail App Extensions, Plug-Ins Will Stop Functioning in Future Release

As part of WWDC this week, Apple introduced a new MailKit framework for macOS Monterey that enables developers to create Mail app extensions that block content, perform message and composing actions, and help with security.

mail app extensions macos monterey
There will be four main categories of Mail app extensions, according to Apple:

  • Compose: Extensions that provide new workflows when composing emails
  • Actions: Extensions that apply custom rules to incoming emails, such as an email being color coded, moved to a separate inbox, marked as read, or flagged
  • Content Blocking: Extensions that serve as WebKit content blockers for emails based on specific criteria in an email's HTML code
  • Message Security: Extensions that sign, encrypt, and decrypt emails when sending and receiving mail, with signed and encrypted icons below emails

Xcode 13, available in beta, includes a template for developers looking to create Mail app extensions on the Mac. The extensions can be built into existing Mac apps and can also be distributed through the Mac App Store, according to a WWDC session about MailKit, which is available on macOS only and not iOS or iPadOS.

In the WWDC session, Apple indicated that older Mail app plug-ins will stop functioning in an unspecified future macOS release.

macOS Monterey is available now in beta for developers, with a public beta to follow in July.

Related Forum: macOS Monterey

Popular Stories

iOS 26

iOS 26.2 Available Next Month With These 8 New Features

Tuesday November 11, 2025 9:48 am PST by
Apple released the first iOS 26.2 beta last week. The upcoming update includes a handful of new features and changes on the iPhone, including a new Liquid Glass slider for the Lock Screen's clock, offline lyrics in Apple Music, and more. In a recent press release, Apple confirmed that iOS 26.2 will be released to all users in December, but it did not provide a specific release date....
m1 chip slide

Five Years of Apple Silicon: M1 to M5 Performance Comparison

Monday November 10, 2025 1:08 pm PST by
Today marks the fifth anniversary of the Apple silicon chip that replaced Intel chips in Apple's Mac lineup. The first Apple silicon chip, the M1, was unveiled on November 10, 2020. The M1 debuted in the MacBook Air, Mac mini, and 13-inch MacBook Pro. The M1 chip was impressive when it launched, featuring the "world's fastest CPU core" and industry-leading performance per watt, and it's only ...
AirPods Pro Firmware Feature

Apple Releases New Firmware for AirPods Pro 2, AirPods Pro 3, and AirPods 4

Thursday November 13, 2025 11:35 am PST by
Apple today released new firmware designed for the AirPods Pro 3, the AirPods 4, and the prior-generation AirPods Pro 2. The AirPods Pro 3 firmware is 8B25, while the AirPods Pro 2 and AirPods 4 firmware is 8B21, all up from the prior 8A358 firmware released in October. There's no word on what's include in the updated firmware, but the AirPods Pro 2, AirPods 4 with ANC, and AirPods Pro 3...
iphone pocket%402x

Apple Debuts iPhone Pocket, a Limited Edition iPod Sock-Style Accessory

Tuesday November 11, 2025 1:23 am PST by
Apple has teamed up with Japanese fashion house ISSEY MIYAKE to launch iPhone Pocket, a 3D-knitted limited edition accessory designed to carry an iPhone, AirPods, and other everyday items. The accessory is like a stretchy pocket, not unlike an iPod Sock, but elongated to form a strap made of a ribbed, elastic textile that fully encloses an iPhone yet allows you to glimpse the display...
homepod mini colors

New HomePod Mini Coming Soon With These Features

Tuesday November 11, 2025 7:30 am PST by
Apple is expected to announce a new HomePod mini imminently, headlining with new chips. Here are all of the new features we're expecting. The second-generation HomePod mini is highly likely to contain a more up-to-date chip for more advanced computational audio and improved responsiveness. The current HomePod mini is equipped with the Apple Watch Series 5's S5 chip from 2019. Apple is likely ...
ios 26 digital id passport wallet

Apple Announces Launch of U.S. Passport Feature in iPhone's Wallet App

Wednesday November 12, 2025 9:15 am PST by
Apple today announced that iPhone users can now create a Digital ID in the Apple Wallet app based on information from their U.S. passport. To create and present a Digital ID based on a U.S. passport, you need: An iPhone 11 or later running iOS 26.1 or later, or an Apple Watch Series 6 or later running watchOS 26.1 or later Face ID or Touch ID and Bluetooth turned on An Apple Account ...
homepod mini thumb feature

New HomePod Mini, Apple TV, and AirTag Were Expected This Year — Where Are They?

Wednesday November 12, 2025 11:42 am PST by
While it was rumored that Apple planned to release new versions of the HomePod mini, Apple TV, and AirTag this year, it is no longer clear if that will still happen. Back in January, Bloomberg's Mark Gurman said Apple planned to release new HomePod mini and Apple TV models "toward the end of the year," while he at one point expected a new AirTag to launch "around the middle of 2025." Yet,...
Tesla Charging

Tesla Working to Add Apple CarPlay Support to Vehicles

Thursday November 13, 2025 8:31 am PST by
Tesla is working to add support for Apple CarPlay in its vehicles, Bloomberg's Mark Gurman reports. Tesla vehicles rely on its own infotainment software system, which integrates vehicle functions, navigation, music, web browsing, and more. The automaker has been an outlier in foregoing support for Apple CarPlay, which has otherwise become an industry standard feature, allowing users to...
CarPlay Pinned Messages

iOS 26.2 Adds New CarPlay Setting

Thursday November 13, 2025 6:48 am PST by
iOS 26 extended pinned conversations in the Messages app to CarPlay, for quick access to your most frequent chats. However, some drivers may prefer the classic view with a list of individual conversations only, and Apple now lets users choose. Apple released the second beta of iOS 26.2 this week, and it introduces a new CarPlay setting for turning off pinned conversations in the Messages...
iphone air thinness

iPhone Air Sales Are So Bad That Apple's Delaying the Next-Generation Version

Monday November 10, 2025 11:41 am PST by
The thin, light iPhone Air sold so poorly that Apple has decided to delay the launch of the next-generation iPhone Air that was scheduled to come out alongside the iPhone 18 Pro, reports The Information. Apple initially planned to release a new iPhone Air in fall 2026, but now that's not going to happen. Since the iPhone Air launched in September, there have been reports of poor sales...

Top Rated Comments

cmaier Avatar
58 months ago

What we would like to get: correctly working gmail with most of its features in the native mail app
What we are getting:
Who is “we?” People who don’t care about their privacy, who demand that Apple support non-standards based protocols and functionality, and who work at Google?
Score: 24 Votes (Like | Disagree)
countryside Avatar
58 months ago
Can someone make an extension that lets us schedule a time for an email to be sent?
Score: 21 Votes (Like | Disagree)
kc9hzn Avatar
58 months ago

What we would like to get: correctly working gmail with most of its features in the native mail app
What we are getting:
To be fair, that’s mostly the fault of Google’s bizarre non-standard implementation of IMAP. Those features don’t really work on any app other than GMail.

As for the mail plug-ins, they were never a great solution. Apple will continually move away from systems like mail plug-ins that live in the memory space of another application to inter-application communication systems like extensions that allow an application to extend another application visually without sharing memory space MacOS Classic style. I, for one, am looking forward to having a mail extension system that provides a stable API and that doesn’t break with each point release.
Score: 13 Votes (Like | Disagree)
Peepo Avatar
58 months ago
Hope will be possible to tag a sender as not junk.
Score: 10 Votes (Like | Disagree)
kc9hzn Avatar
58 months ago

Same thing, different day, Apple can never find the original team that built a program, so they have to rebuild it from the ground up! lol
You do realize that Mail.app is a direct continuation of the NeXTStep Mail.app, yes? Which means that it’s nearly 40 years old. Most of the original team is probably retired by now.

But this is also a change that needed to occur. Previously, mail bundles would break between point releases. Not major releases, mere patches. Every time Mail.app got updated, these bundles needed to get updated, too, and, until they did, the bundles wouldn’t work. Now we have a stable API guaranteed not to break on point releases and that will likely be stable across multiple major releases. We’ll probably see more mail extensions as a result of this, while previously, it was only worth the effort to devs who were absolutely serious about email extensibility. This API could also be ported to MobileMail.app, which, until now, hasn’t had any extensibility (except maybe for jailbreaking, but even then, I don’t think Mail was a common target for jailbreakers looking to tweak the system).
Score: 6 Votes (Like | Disagree)
Graham King Avatar
58 months ago
It would be nice to be able to easily add HTML signatures. I might switch back from Spark if this is possible.
Score: 4 Votes (Like | Disagree)