The format of this command is: EUID <euid>
- If successful, EUID returns OK followed by a message number. The message is
-*not* guaranteed to exist, because EUID indices are not immediately removed
-when a message is deleted.
+ If successful, EUID returns OK followed by a message number.
If no message exists in the current room with the supplied EUID, the command
returns ERROR+MESSAGE_NOT_FOUND.