Це стара версія документу!
http://wiki2.dovecot.org/
http://wiki2.dovecot.org/QuickConfiguration
http://www.brennan.id.au/12-Sendmail_Server.html
http://www.squirrelmail.org/about/
http://www.openspf.org/
http://www.openspf.org/FAQ/Common_mistakes
http://serverfault.com/questions/369460/what-are-spf-records-and-how-do-i-configure-them