It’s a new year, do you know what your filters are doing?
Yesterday the NJABL domain expired. The list was disabled back in 2013 but the domain continued to be maintained as a live domain. With the expiration, it was picked up by domain squatters and is now listing everything. Steve wrote about how and why expired blocklist domains list the world last year.
The short version is, that when domain squatters grab a domain they put in a DNS entry that responds to every single query. Blocklists work by responding to DNS queries for listed domain. Put those two things together and a domain squatter grabbing a blocklist domain means, effectively, everything is listed.
The squatting happened sometime yesterday. A few people mentioned they were seeing some failures mentioning the list yesterday. One of them commented here.
Replying to an almost 6 year old post might not have many eyes see this, but I’ve just had a weird thing happen and it might help someone. Somewhere over the last 2 days, some people have been getting rejection messages from my Exchange 2010/SBS 2011 server and they finally called me to let me know. I had a few block lists, including dnsbl.njabl.org configured in the Hub Transport/Anti-Spam section from years ago when I set the server up. I disabled NJABL first up, and it all started working again. It had been blocking from people’s work domains to me, as well as hotmail and yahoo emails. All good now.
This is as good a time as any to review your current filter setup. Are all the external filters meeting your needs? Are they still actively maintained? Those of you managing spam assassin, have you upgraded to the recent ruleset, yet? Should you? When was the last time your AV was updated?
While you’re thinking about it, drop a task in your task manager to remind you to check the filters again in 12 months.
These tasks are tedious and easy to drop to the bottom of any todo list. But regular review of filtering is important to maintain the effectiveness of the filters. For instance, anyone running NJABL has been querying a dead list for more than 5 years now. Wasted electrons, electricity and CPU cycles. Maybe it doesn’t seem like much in the grand scheme of things, but it is inefficient and wasteful.
Start the new year off right. Go review your filters. I’m even going to go check my personal filters to see if there are things I can add or remove to make my own mail better.