...
- http://people.apache.org/~dos/sa-plugins/3.0/wrongmx.cf
- http://people.apache.org/~dos/sa-plugins/3.0/wrongmx.pm
How To Use It
Save the two files above in your local configuration directory (/etc/mail/spamassassin/) and set the score in wrongmx.cf to whatever you desire, based on your confidence in your primary MX server stability.
...
Do not use this plugin on overloaded mail systems that frequently stop accepting connections on the primary MX servers due to system load since it will cause some false positives if you set the score too high.