Custom email domain keeps disappearing
On my Mac, the ability to send emails from my custom email domain account keeps disappearing in the mail app - and on iCloud.com.
One day it's there, the next it isn't.
Meanwhile, this doesn't happen on my iPhone.
I can receive email just fine, but there appears to be absolutely no way to compose email for my custom account on my Mac or via iCloud.com when it disappears.
Sometimes logging out of my iCloud account works, other times it doesn't.
MacBook Pro Apple Silicon