Deleting mails not possible in mail on my Mac book.
I could not delete mails on my MacBook, or not send mails. So mail wouldn't work at all. On my iPhone no problem.
After reinstalling Monterey the problem wasn't solved.
But when you go to mail, preferences, accounts, and then server then you can choose another smtp server.
Send a testmail and than you re-install the cloud server.
And all was updated and mail works how it should.
So for me the problem was solved.