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…
Category: RBL
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AT&T rbl block inquiry site
First, I guess I should give a primer, what’s an RBL? RBL stands for Realtime Black List (or Realtime Block List depending on who you talk to.) The idea is there are machines that either 1) have no business DIRECTLY trying to deliver a mail message to a legitimate mail server or 2) are known to spew out junk mail, or viruses or other bad content. So, many service providers make use of blacklists to decline messages from suspect machines. In some cases these lists are cultivated in house, in other cases people make use of various publicly available lists online.
But…