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 16 Pro Sizes Feature

iPhone 16 Launch Is Just One Month Out – Here's Everything We Know

Saturday August 10, 2024 5:00 am PDT by
Apple typically releases its new iPhone series in the fall, and a possible September 10 announcement date has been floated this year, which means we are just one month away from the launch of the iPhone 16. Like the iPhone 15 series, this year's lineup is expected to stick with four models – iPhone 16, iPhone 16 Plus, iPhone 16 Pro, and iPhone 16 Pro Max – although there are plenty of design...
macbook pro bb cyber

Apple's M3 MacBook Pro Gets Up to $1,000 Off In Major New Sales, Starting at $1,299 [Updated]

Sunday August 11, 2024 1:54 pm PDT by
Apple's M3 MacBook Pro is seeing multiple high value discounts on Best Buy and Amazon today, with up to $1,000 off select models. This includes a new all-time low price on the entry-level M3 512GB 14-inch MacBook Pro at $1,299.00, down from $1,599.00, and a massive $1,000 discount on the high-end 16-inch model exclusively for Best Buy members. Note: MacRumors is an affiliate partner with Best...
iPhone 16 Pro Right Side Feature

The iPhone 16 is Getting a New Button: Here's What It Can Do

Tuesday August 13, 2024 4:01 pm PDT by
Multiple rumors have suggested that the iPhone 16 models are going to have an all-new button that's designed to make it easier to capture photos when the devices are held in landscape mode. Apple calls the button the Capture Button internally, and it is going to be one of the most advanced buttons that's been introduced to date with support for multiple gestures and the ability to respond to ...
iOS 18 on iPhone Feature

Everything New in iOS 18.1 Beta 2 and iOS 18 Beta 6

Monday August 12, 2024 2:32 pm PDT by
Apple is beta testing iOS 18 and the first update to iOS 18 concurrently, and we got the second betas of iOS 18.1, iPadOS 18.1, and macOS Sequoia 15.1 today alongside the sixth betas of iOS 18, iPadOS 18, and macOS Sequoia 15. Many of the changes in iOS 18.1 are focused on bringing the .1 betas in line with the standard betas, which recently received updates to Photos and Safari, while...
Beyond iPhone 13 Better Blue Face ID Single Camera Hole

10 Reasons to Wait for Next Year's iPhone 17

Thursday August 8, 2024 4:40 am PDT by
Apple's iPhone development roadmap runs several years into the future and the company is continually working with suppliers on several successive iPhone models simultaneously, which is why we sometimes get rumored feature leaks so far ahead of launch. The iPhone 17 series is no different – already we have some idea of what to expect from Apple's 2025 smartphone lineup. If you plan to skip...
iPhone 17 Slim Feature Single Camera 2

Next Year's Slim iPhone 17 Could Be an 'iPhone Air'

Monday August 12, 2024 8:43 am PDT by
Apple's rumored iPhone 17 "Slim" could be positioned as an iPhone "Air" to boost sales, according to Bloomberg's Mark Gurman. In the latest edition of his "Power On" newsletter, Gurman explained how the "fourth" model in the iPhone lineup since 2020 (the iPhone 12 mini, iPhone 13 mini, iPhone 14 Plus, and iPhone 15 Plus) has largely been a commercial failure. In the case of the Plus model,...

Top Rated Comments

cmaier Avatar
42 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
42 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
42 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
42 months ago
Hope will be possible to tag a sender as not junk.
Score: 10 Votes (Like | Disagree)
kc9hzn Avatar
42 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
42 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)