I can usually tell when one of the ISPs makes some change to their incoming spam filtering just by my call volume. The past few weeks the ISP in most of my calls has been Comcast. And, what do you know, they have made changes to how they are filtering email.
According to their bounce message, Comcast is using ReturnPath’s proprietary SenderScore product to filter mail. Reports on thresholds vary, but IPs with SenderScores of 70 and below have been blocked with messages similar to:
Remote host said: 554 IMTA06.emeryville.ca.mail.comcast.net comcast
10.01.01.01 Comcast BL009 Blocked for spam. Please see
In addition to blocking based on SenderScore, Comcast also appears to be blocking based on complaints from their users. Comcast is testing a feedback loop. I have heard from one FBL user that there are some kinks to work out, but that the FBL provider is working with them to resolve the problems.
This new process is a complete change from the previous way Comcast handled email blocking. Previously they were primarily using Brightmail to filter spam from their mail stream, now they are using complaints to identify bad mail. During the the transition mailers are seeing an increase in blocked email.
There are solutions. Use the forms Comcast directs you to use when they reject your mail. If there are extensive problems, talk to your delivery monitoring company or your delivery consultant. Most of us have the ability to escalate issues and talk to people internal to ISPs in order to determine if there is some specific problem and what you can do about it. But, don’t panic, Comcast doesn’t hate you, in fact, I expect these changes are going to better for everyone in the long run.