As of 2.0.12, looks like NONEXISTENT response code isn't working properly again. Previously brought up issues relating to this here: http://markmail.org/message/jxbgdfv26pws66og With a nonexistent mailbox "FOO", I see this: 1 DELETE "FOO" 1 NO Mailbox doesn't exist: FOO // Should be: 1 NO [NONEXISTENT] Mailbox doesn't exist: FOO 2 RENAME "FOO" "BAR" 2 NO Mailbox doesn't exist: FOO // Should be: 2 NO [NONEXISTENT] Mailbox doesn't exist: FOO michael