It’s unusual for mail servers to suddenly start rejecting messages internally and from external sources. That’s exactly what I saw though over the weekend. A mailserver running mdaemon on Windows 2000 was rejected ALMOST every message that was sent it’s way whether it was an internal mail sender and recipient or external sender to internal recipient. The really interesting things was to see a message sporadically succeed. This problem was with mdaemon, but could have occured with ANY mail server. Here’s why…
Tag: ordb
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More postfix spam blocking….
Postfix has a NUMBER of tools for rejecting unwanted messages before they get in the door and waste your CPU time on deciding “hey this mail is spam”. Up until recently I’ve mostly used the relays.ordb.org check (which in the last couple months has now gone defunct.) When we started noticing problems with ordb.org’s responsiveness I planned to investigate other blacklisting options and found several. Obviously there are advantages and disadvantages to blacklisting. The first disadvantage is you have turned over control of blocking mail senders to an outside authority and you should familiarize yourself with THEIR policies for listing (and delisting) a server.
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Is something up with ordb.org?
I’ve noticed several times in the last week a server of mine that is using postfix has rejected messages due to a failure in the lookup at relays.ordb.org. At first, I thought this was just a false positive in the database at ordb… but this morning I finally “caught it” while it was happening and went to pull up the ordb.org web page. It took…. 30-45 seconds and then proceeding to do a search on the rejected IP took another stretch. In looking at the logs it appears that there may be blanket rejections if the ordb.org check times out.
Here’s the postfix config setting….
smtpd_client_restrictions = permit_mynetworks,reject_rbl_client relays.ordb.org