If you plan to upgrade to macOS Sonoma later this year but also happen to make use of legacy Mail plug-ins, you're going to be in for a bad time. That's because the update will remove support for those plug-ins for the first time.
Plug-ins can be used for a variety of things, like bulk email management and automation. They can often be used by businesses and power users and now it appears that they're going to have to consider upgrading to something newer or ditching those plugins and their features altogether.
