Troubleshooting: part 3

As I continue to think about how people troubleshoot email delivery I keep finding other things to talk about. Today we’re going to talk about the question most folks start with when troubleshooting delivery. “Did ISP change something?”

image of a head with gears and ideas floating around it

At least once a week I check some delivery or email fora and some form of the question is sitting there.

“Did X change something? We haven’t done anything different and our delivery went way down overnight.”

Did Y change their filters? Our delivery is tanking and all our authentication is fine.”

Anyone hear of a change at Z? We have been having increasing difficulty reaching the inbox and we don’t understand why. Looking for suggestions.

In reality, the answer to this question Does Not Matter and asking it is only going to delay actually resolving your delivery issue.

When filters change

The reality is, filters are continually changing. ISPs and filtering companies are always tuning filters. These changes are roughly in 3 categories.

  • Ongoing tweaking and improvement to provide a better experience for their users
  • Changes done to address a emergent threat (Yahoo deploying p=reject is one example of this)
  • Specific changes to catch a type of spam they had previously been unable to effectively identify and filter.

Filters are not static. They are continually adjusting based on a number of things. We can always assume the answer to the question is yes. Something changed. Now what?

There are basically 3 situations here.

  • The filters did something unexpected and caught mail it wasn’t intended to catch, causing recipients to complain to the ISP.
  • The filter change was intentional but caught more mail than was intended, causing recipients to complain to the ISP.
  • The filter change was intentional and caught exactly the mail that was intended and the recipients didn’t care enough to notice that mail was missing.

In the first two cases, the ISP is going to fix things. They’re going to listen to their users and adjust the filters. In the first case, I expect to see changes and rollback within 24 – 48 hours. In the second, I expect to see changes in 24 – 96 hours.

The third case is the interesting one. Does anyone care about mail they don’t care about going to the bulk folder? Folks sending mail, even opt-in mail, that the users don’t complain about when it’s missing is the definition of grey mail. Filter maintainers listen to their users. If users complain they’ll change things, if users don’t complain they’ll assume the filters are working as intended.

The answer to the question did the filters changed tells you nothing. Of course the filters changed. Either they’re doing something that the maintainers don’t intend, which means they’ll be fixed or they’re catching mail they’re intended to catch.

Instead of asking if the filters changed, flip the question. Why are my users not interested enough in my mail to notice it when it’s gone? Start your troubleshooting from that perspective.

What about the email client?
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Who are mimecast?

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Earlier today someone asked on Facebook if mimecast may be blocking emails based on the TLD. The short answer is it’s unlikely. I’ve not seen huge issues with them blocking based on TLD of the domain. They’re generally more selective than that.

The good news is mimecast is really pretty good about giving you explanations for why they’re blocking. They’ll even tell you if it’s mimecast related or if it’s a specific user / user-company block.
Some example rejection messages from a recent dive into some bounce logs.

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Troubleshooting delivery is hard, but doable

Even for those of us who’ve been around for a while, and who have a lot of experience troubleshooting delivery problems things are getting harder. It used to be we could identify some thing about an email and if that thing was removed then the email would get to the inbox. Often this was a domain or a URL in the message that was triggering bulk foldering.
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It seemed that one mailing was really bad and resulted in a bad reputation, temporarily. But as the client fixed the problem and kept mailing their reputation recovered.
Deliverability troubleshooting is complicated and this flowchart sums up what it’s like.

Here at Word to the Wise, we get a lot of clients who have gone through the troubleshooting available through their ESPs and sometimes even other deliverability consultants. We get the tough cases that aren’t easy to figure out.
What we do is start from the beginning. First thing is to confirm that there aren’t technical problems, and generally we’ll find some minor problems that should be fixed, but aren’t enough to cause delivery problems. Then we look at the client’s data. How do they collect it? How do they maintain it? What are they doing that allows false addresses on their list?
Once we have a feel for their data processes, we move on to how do we fix those processes. What can we do to collect better, cleaner data in the future? How can we improve their processes so all their recipients tell the ISP that this is wanted mail?
The challenging part is what to do with existing data, but we work with clients individually to make sure that bad addresses are expunged and good addresses are kept.
Our solutions aren’t simple. They’re not easy. But for clients who listen to us and implement our recommendations it’s worth it. Their mail gets into the inbox and deliverability becomes a solved problem.

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A DNSBL works like this, a mail server checks the sender’s IP address of every inbound email against a blacklist and the blacklist responses with either, yes that IP address is on the blacklist or no I did not find that IP address on the list.  If an IP address is found on the list, the email administrator, based on the policies setup on their server, can take a number of actions such as rejecting the message, quarantining the message, or increasing the spam score of the email.
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Maintaining a DNSBL is a lot of work and after years of providing a valuable service, you are thanked with the difficulties with decommissioning the list.  Popular DNSBLs like the AHBL list are used by thousands of administrators and it is a tough task to get them to all stop using the list.  RFC6471 has a number of recommendations such as increasing the delay in how long it takes to respond to a query but this does not stop people from using the list.  You could change the page responding to the site to advise people the list is no longer valid, but unlike when you surf the web and come across a 404 page, a computer does not mind checking the same 404 page over and over.
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So spread the word,

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