It may already be there (I can't find it, or any mention of "sound" or "bell" in the help).... so if it is, just point the way. If not:

Feature-request: I would like to be able to specify what sound is played when the bell is transmitted to the client. Right now, it's a sound that means "error" on everything else that is running. Everytime I receive e-mail in Pine, it sounds like a major connection problem happened in one of six other programs running. 😡

I could make the 'bell' sound configurable. However, I'd caution against changing it to 'you've got mail'. If you do, every time you hear a bell for any reason in the terminal, you'll get the mail alert.