SPF并不总只是一种公德性的行为，有时它也会给你带来额外的好处，比如：

Dec 17 15:40:55 tarsier postfix/smtpd

\[63579\]

: NOQUEUE: reject: RCPT from unknown

\[60.177.46.2\]

: 550 support@geekcn.org: Sender address rejected: “geekcn.org

\[60.177.46.2\]

is not allowed to send mail for support@geekcn.org”; from=support@geekcn.org to=steve@geekcn.org proto=ESMTP helo=<geekcn.org>