Jeremy Zawodny has a very short and to the point explanation on his blog
, and there are a several different scripts/programs that beautify or enhance the emails sent - cvscommit
(all changes in one single mail), CVSspam
(colorize and tag as non-spam to SpamAssassin), and if you Google I'm sure you find several others.
Also make sure you have upgraded to cvs 1.11.16 since older versions have an exploitable security problem.