Mark
From MUME
This command can be used to mark a message on a bulletin board that you wish to remember.
Usage: mark <number>
Messages marked like this are still displayed by 'look board' even if they have been read (they are marked with a '*' after the message number). You can use 'unmark <number>' to remove the mark. 'mark last' and 'unmark last' can also be used.
