The messages you receive are kept in a file called mbox. To see a list of all the messages on file, type headers all at the MM> prompt. In the following example, there are 6 messages.
MM>headers all 1) 19-Jun Fuat C. Baran New stuff in MM (317 chars) 2) 19-Jun Melissa Metz charges (1620 chars) 3) 20-Jun Joe Brennan corrupted mbox (2285 chars) A 4) 21-Jun Sue Zayac another thing (251 chars) 5) 21-Jun Howie Kaye quota (5258 chars) 6) 21-Jun Don Lanini Emacs question (1036 chars) MM>
To read a particular message, type read and the message number, at the MM> prompt. For example, to see Melissa Metz's message about charges, type read 2:
MM>read 2
To delete a message you no longer need, you can type delete or d at the R> prompt, right after reading it, or type delete and the message number at the MM> prompt:
MM>delete 2 2 MM>
Deleting does not erase the message; it just marks it as deleted. Another command, expunge, removes all deleted messages permanently:
MM>expunge MM>
You may not have to use the expunge command. If you leave MM with the bye command, it will ask whether you would like to expunge; if you leave with the exit command, it expunges automatically.
Try to delete and expunge regularly. If you have let it go, use headers and read to go over your old messages, delete any you don't need any more (or move them to other mail files), and expunge. You'll find MM runs faster and more efficiently with smaller mail files.