Kris writes, "Hi Al, I am contacting you because I would like to receive some feedback (advice, tips) on how an ISP can help to prevent outbound spam.
"I work for an ISP in the Netherlands. Inbound spam isn't much of a problem for us, this is usually handled well by DNSBLs and filters. However, outbound spam is a problem. As we don't have any control over all the servers operating within our IP space, nor do we have the processing power to filter all outbound e-mail, we rely heavily on automated abuse reports to identify spam problems. These automated responses can really accumulate and clog up a ticketing system like RT. Instead of trying to remove out all the duplicate reports for a single IP address, I decided to aggregate those reports based on the source IP address of the spam. Now I have come to a point where I have a system that can do just that and a bit more, but I'm running out of ideas to effectively minimize spam originating from my network. Perhaps you could share your thoughts."
Kris, thanks for writing. I know that proactively monitoring, mitigating or preventing outbound spam is a huge challenge for ISPs. I deal with it from the ESP side of things, where it is very complex, and over on your side of things, it is probably even more complex. I don't think I have much useful advice to give on the topic, so I'm posting this with the hope that you, dear readers, will step up and share some of your thoughts on best practices for an ISP as far as mitigating outbound abuse.
(One thing I would suggest is checking out a more robust, abuse-specific ticketing system, such as Abacus.)