The long tail of domains

I frequently get clients telling me that they have about 15 (20, 30) major domains on their list, and then a long tail of domains with only a couple of recipients. If you sort simply by the left hand side of the @, that’s true.
When you’re sending email, it’s not just the domain in the email address that is important. Of equal importance is the MX. The MX is what actually handles the mail and where many filters are applied. Sorting by MX, instead of simply recipient domain, can identify that most of your small business clients are hosted at a particular provider. The number of subscribers behind that filter may be enough to push that filter into your top 10 or even top 5 recipient domains.
There’s a much smaller tail when grouping recipients by MX domain. It makes it much easier to understand where blocks are happening. I have even seen cases where clients didn’t realize they were blocked at a commercial provider because they only saw the “onesie twosie” domains as undeliverable. They missed a real problem with blocking because they were looking at the wrong data.
I sometimes get the side eye from some ISP folks if I use the term receiver (because, well, they’re senders as much as they are receivers). But I use receiver to help distinguish between the recipient domain and the actual domain handling the email.
When was the last time you looked at your delivery by filter or MX rather than by recipient domain? What did you find?

Related Posts

Incorrect rejection messages

At least one ESP and Spamhaus are currently investigating bounce messages at a couple ISPs incorrectly pointing to Spamhaus as the reason for the block. The bounce messages are taking the form:

Read More

Filtering secret sauce

It seems one of the most asked questions I hear from people is about filters and what the secret sauce is.

Read More

Typo traps

People make all sorts of claims about typo traps. One claim that showed up recently was that Spamhaus has just started using typo traps. I asked my Facebook network when people started using typos to detect incoming spam.
Two different colleagues mentioned using typos, both on the left hand side and the right hand side, back in ’98 and ’99.
The point is, typo traps are absolutely nothing new. They are, in fact, as old as spam filtering itself. And as one of trap maintainers remind me, not all of them even look like typos. It’s not as simple as hotmial.com or gmial.com.
I really think that focusing on traps is paying attention to the wrong thing.
The traps are not the issue. The underlying issue is that people are signing up addresses that don’t belong to them. Sometimes those are addresses that are spamtraps. Sometimes those are simply addresses that belong to someone else. Those addresses don’t belong to customers, they belong to random people who may never have heard of the sender. Sending mail to those people is sending spam.
Just trying to remove traps from your address lists isn’t going to solve the underlying problem. Instead, focus on improving your data process to keep from sending mail to random strangers.

Read More