Decrypted messages should never be stored on the IMAP server. That is pretty much the whole thing here. It overtly defeats the PGP encrypt once scheme. In the

Decrypted messages should never be stored on the IMAP server. That is pretty much the whole thing here. It overtly defeats the PGP encrypt once scheme. In the same way, a user intending to send an encrypted email should be able to be confident that the email client will not automatically save an unencrypted message to some sort of Drafts folder on the IMAP server.