I added a couple lines to .muttrc as recommended (I had most but not all 
those lines).
Now I don't get the Message Undeliverable emails, but they still don't 
get through.  Except one.  I sent a test mail to all of my U of M 
accounts (I have three) and one got through.  I got so excited and 
started sending more mails but none of them got through.

As for what I have in the local-host-names file, I put 'slava.net' 
because that's what's at the end of my email address... that's my 
homepage and so on.  What should be there?

Lorry, who has said '$&%* it' and is using Mozilla until this gets sorted