I ran 'cvs update' after a long drought and suddenly couldn't send any
mail!  I tracked this down to a change in smtpmail.el that sets the
coding system on outgoing mail buffers; it calls
set-buffer-file-coding-system with four arguments, but my Emacs ("GNU
Emacs 21.4.1 (sparc-sun-solaris2.10, X toolkit) of 2005-05-31 on
maytag.mit.edu") only takes three.

To make things work I needed the following: