Cannot enable or disable Mail plug-ins I have two Mail.app plug-ins installed: "GPGMailLoader.mailbundle" and "Smallcubed MailSuite.mailbundle".  Currenly, GPG is enabled, and works, and MailSuite is disabled.

However, when I toggle either plugin (i.e. MailSuite to on or GPG to off), and restart Mail, the change hasn't taken.  So I cannot use MailSuite, nor disable GPG.

I have tried:


Reinstalling MacOS Mojave in-place (did not fix).
Creating a new user (everything works for new user).


How can I further investigate this?
Eventually I moved my ~/Library/Mail folder to the Desktop, reset mail "to factory settings", then re-imported all messages from the moved folder.  It took about a day, including the backup I did first.

Following the above "reset" instructions involves deleting ~/Library/Containers/com.apple.mail/.  When I was perusing the new ~/Library/* and ~/Library/Containers/com.apple.mail/* setup, after relaunching Mail, there were differences before and after, in particular which items lived in the container and which lived in the real ~/Library.  This may be a clue to a cause, but at least there is now a sledgehammer solution.