The svnmailer is a tool, which is usually called by a Subversion hook to submit commit notifications in various ways (at the moment: mail via SMTP or a pipe to a sendmail like program, news via NNTP, CIA live tracker notification via XML-RPC). It is derived from the original mailer.py distributed with Subversion, but supposed to be much more consistent, better extensible and to have much more features. Have a look at the documentation for further details.