If you use squirrelmail, you can send messages with wget. This avoids many anti-spam and configuration issues.

wget --save-cookies cookies.txt --keep-session-cookies --post-data 'login_username=username&secretkey=password' http://webmail.server.com/src/redirect.php

wget --load-cookies cookies.txt --post-data 'body=body here&send_to=recipient%40wherever.com&subject=subject here&send=1' http://webmail.server.com/src/compose.php

For a bit more, see:

http://mikemccabe.wordpress.com/2007/08/07/sending-email-wit...