Path: utzoo!utgpu!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!rutgers!apple!bbn!gateway!nucst4.neep.wisc.EDU!simmons
From: simmons@nucst4.neep.wisc.EDU (kim h simmons)
Newsgroups: comp.emacs
Subject: Finding out when new mail has arrived
Message-ID: <8812180059.AA04299@nucst4.neep.wisc.edu>
Date: 18 Dec 88 00:59:45 GMT
References: <1466@zen.UUCP>
Sender: news@bbn.COM
Organization: BBN news/mail gateway
Lines: 2

I think that the word 'Mail' appears in the mode line if there is mail 
that you have not read yet.