This signature triggers on a normal EXAMINE INBOX command. Won't the following regex fire on any imap EXAMINE command and not just "examine..256+"? Can this be combined with the "min match length" to fix?
[0-9][\x20][Ee][Xx][Aa][Mm][Ii][Nn][Ee][\x20][^\x0a\x0d]+[\x0a\x0d]