MailSuite will not work with Sonoma - macOS 14
Apple has permanently disabled the ability to load any Mail plugin in macOS 14.
MailSuite and Sonoma 😢
Apple announced it would stop allowing Mail plugins in a future operating system when it announced macOS 11 (Big Sur) in 2021. That time has come. Although it has not made a formal announcement, Mail on macOS 14 (Sonoma) will no longer load Mail Plugins.
About Mail Extensions
To provide an alternative to plugins, Apple introduced Mail Extensions in 2021. However, extensions' access to Mail is nowhere near enough to facilitate the functionality needed for MailSuite’s components to work within Mail.
As an analogy, Mail Plugins invited developers into Mail like a roommate. They could make themselves at home, change the look and feel a bit, add some of their own stuff, and rearrange the furniture. Mail Extensions, on the other hand, ask the developer to wait at the door and respond to specific requests Mail makes.
There is no mechanism to add tags to messages so that they appear in the Snippet or List view. Extensions cannot apply rules to outgoing messages. They cannot set up a separate window to display selected messages, and Mail Extensions cannot change email signatures—all things MailSuite needs to work.
