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

iPhone 17 Pro in Hand Feature Lowgo

iPhone 17 Pro to Reverse iPhone X Design Decision

Monday July 7, 2025 9:46 am PDT by
Since the iPhone X in 2017, all of Apple's highest-end iPhone models have featured either stainless steel or titanium frames, but it has now been rumored that this design decision will be coming to an end with the iPhone 17 Pro models later this year. In a post on Chinese social media platform Weibo today, the account Instant Digital said that the iPhone 17 Pro models will have an aluminum...
iOS 26 Feature

Everything New in iOS 26 Beta 3

Monday July 7, 2025 1:20 pm PDT by
Apple is continuing to refine and update iOS 26, and beta three features smaller changes than we saw in beta 2, plus further tweaks to the Liquid Glass design. Apple is gearing up for the next phase of beta testing, and the company has promised that a public beta is set to come out in July. Transparency In some apps like Apple Music, Podcasts, and the App Store, Apple has toned down the...
imac video apple feature

Apple Launching These 15+ Products Later This Year

Sunday July 6, 2025 8:05 am PDT by
The calendar has turned to July, meaning that 2025 is now more than half over. And while the summer months are often quiet for Apple, the company still has more than a dozen products coming later this year, according to rumors. Below, we have outlined at least 15 new Apple products that are expected to launch later this year, along with key rumored features for each. iPhone 17 Series iPho...
iphone 16 pro models 1

Here's How the iPhone 17 Pro Max Will Compare to the iPhone 17 Pro

Saturday July 5, 2025 1:00 pm PDT by
Apple should unveil the iPhone 17 series in September, and there might be one bigger difference between the Pro and Pro Max models this year. As always, the Pro Max model will be larger than the Pro model:iPhone 17 Pro: 6.3-inch display iPhone 17 Pro Max: 6.9-inch displayGiven the Pro Max is physically larger than the Pro, it has more internal space, allowing for a larger battery and...
iPhone Car Key Kia

Here's Which Vehicles Offer iPhone Car Keys

Sunday July 6, 2025 3:03 pm PDT by
In 2020, Apple added a digital car key feature to its Wallet app, allowing users to lock, unlock, and start a compatible vehicle with an iPhone or Apple Watch. The feature is currently offered by select automakers, including Audi, BMW, Hyundai, Kia, Genesis, Mercedes-Benz, Volvo, and a handful of others, and it is set to expand further. Apple has a web page with a list of vehicle models that ...
apple wallet drivers license feature iPhone 15 pro

Apple Says iPhone Driver's Licenses Will Expand to These 8 U.S. States

Tuesday July 8, 2025 11:26 am PDT by
In select U.S. states, residents can add their driver's license or state ID to the Wallet app on the iPhone and Apple Watch, providing a convenient and contactless way to display proof of identity or age at select airports and businesses, and in select apps. Unfortunately, this feature continues to roll out very slowly since it was announced in 2021, with only nine U.S. states, Puerto Rico,...
iphone 17 pro render majin bu

New iPhone 17 Pro Renders Highlight Apple Logo and MagSafe Design Changes

Sunday July 6, 2025 8:43 pm PDT by
New renders today provide the best look yet relocated Apple logo and redesigned MagSafe magnet array of the iPhone 17 Pro and iPhone 17 Pro Max. Image via Majin Bu. Several of the design changes coming to the iPhone 17 Pro model have been rumored for some time, such as the elongated camera bump that spans the full width of the device, with the LiDAR Scanner and flash moving to the right side. ...
apple account card feature

Apple Account Card Expanding to More Countries

Tuesday July 8, 2025 7:34 pm PDT by
Apple is expanding the ability to add an Apple Account Card to the Wallet app to more countries, according to backend Apple Pay changes. With iOS 15.5, Apple updated the Wallet app to allow users to add an Apple Account Card, which displays the Apple credit balance associated with an Apple ID. If you receive an Apple gift card, for example, it is added to an Apple Account that is also...
iPhone 17 Pro in Hand Feature Lowgo

iPhone 17 Pro Coming Soon With These 14 New Features

Friday July 4, 2025 1:05 pm PDT by
Apple's next-generation iPhone 17 Pro and iPhone 17 Pro Max are just over two months away, and there are plenty of rumors about the devices. Below, we recap key changes rumored for the iPhone 17 Pro models. Latest Rumors These rumors surfaced in June and July:Apple logo repositioned: Apple's logo may have a lower position on the back of the iPhone 17 Pro models, compared to previous...

Top Rated Comments

cmaier Avatar
53 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
53 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
53 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
53 months ago
Hope will be possible to tag a sender as not junk.
Score: 10 Votes (Like | Disagree)
kc9hzn Avatar
53 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
53 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)