MTA

Undelivered mail without a bounce

A few weeks ago I wrote a blog post focusing on one small part of bounce handling. Today I want to talk about delivery failures that aren’t bounces. This is really the biggest issue for companies who have written their own bulk sending servers. Modern bulk MTA appliances and ESPs correctly handle these types of bounces. However, when you’re troubleshooting it’s important to know that sometimes there won’t be a SMTP level bounce.

About that DMARC "exploit"

A security researcher has identified a rendering flaw that allows for “perfect” phishing emails. From his website:

MessageSystems Acquires Port25

This morning MessageSystems announced they had acquired Port25 systems. These two platforms were some of the powerhouse brands in the email space. Momentum was the system used by big programs that needed precise control over all their mail from many different streams. Port25 was a lower cost but still powerful system that was accessible to many different size companies.
This acquisition gives MessageSystems the ability to address both market segments.
Port25 staff are all part of the acquisition and the software will continue to be developed and maintained as a separate product from the Momentum line. I, for one, am relieved to hear that. Port25 is a solid piece of software that meets the sending needs of many small and medium size companies.
Congratulations to the great folks at MessageSystems and Port25. I’m excited to see what happens with both programs under the same roof.

Updates to commercial MTAs

Last week Message Systems announced the release of Momentum 4. This high volume MTA has a large number of features that make it possible for large volume senders to manage their email and their delivery. I had the opportunity to get a preview of the new features and was quite impressed with the expanded features. Improvements that caught my eye include:

You can't technical yourself out of delivery problems

In many cases these days, many more cases than a lot of senders want to admit, delivery problems at the big ISPs are a result of sending mail recipients just don’t care about. The reason your mail is going to bulk? It’s not because you have minor problems in your headers. It’s not because you have some formatting issues. The reason is because your recipients just don’t care if the ISP delivers your mail or not.
A few years ago the bulk of my clients hired me to do technical audits for their mail. I fixed a lot of delivery problems that way. They’d send me their email and I’d run it through tools here and identify things they were doing that were likely to be causing problems. I’d give them some suggestions of things to change. Believe it or not, minor tweaks to headers and configuration actually did make a lot of difference in delivery.
Over time, though those tweaks less effective to fix delivery problems. Some of it is due to the MTA vendors, they’re a lot better at sending technically correct mail than they were before. There are also a lot more people giving good advice on the underlying structure and format of emails so senders can send technically clean email. I started seeing technically perfect emails from clients who were seeing major delivery problems.
There are a number of reasons that technical fixes don’t work like they used to. The short version, though, is that ISPs have dealt with much of the really blatant spam and they can focus more time and energy on the “grey mail”.
This makes my job a little harder. I can no longer just look at an email, maybe run it through some of our tools and provide a few suggestions that fix delivery problems. Delivery isn’t that simple any longer. Filters are really more focused on how the recipients react to mail. That means I need to know a lot more about a clients email program before I can even start to identify what might be causing the delivery issues.
I wish it were still so simple I could give minor technical tweaks that would appear to magically improve a client’s delivery. It was a lot simpler process then. But filters have evolved, and senders must evolve, too.

Why do ISPs do that?

One of the most common things I hear is “but why does the ISP do it that way?” The generic answer for that question is: because it works for them and meets their needs. Anyone designing a mail system has to implement some sort of spam filtering and will have to accept the potential for lost mail. Even the those recipients who runs no software filtering may lose mail. Their spamfilter is the delete key and sometimes they’ll delete a real mail.
Every mailserver admin, whether managing a MTA for a corporation, an ISP or themselves inevitably looks at the question of false positives and false negatives. Some are more sensitive to false negatives and would rather block real mail than have to wade through a mailbox full of spam. Others are more sensitive to false positives and would rather deal with unfiltered spam than risk losing mail.
At the ISPs, many of these decisions aren’t made by one person, but the decisions are driven by the business philosophy, requirements and technology. The different consumer ISPs have different philosophies and these show in their spamfiltering.
Gmail, for instance, has a lot of faith in their ability to sort, classify and rank text. This is, after all, what Google does. Therefore, they accept most of the email delivered to Gmail users and then sort after the fact. This fits their technology, their available resources and their business philosophy. They leave as much filtering at the enduser level as they can.
Yahoo, on the other hand, chooses to filter mail at the MTA. While their spamfoldering algorithms are good, they don’t want to waste CPU and filtering effort on mail that they think may be spam. So, they choose to block heavily at the edge, going so far as to rate limit senders that they don’t know about the mail. Endusers are protected from malicious mail and senders have the ability to retry mail until it is accepted.
The same types of entries could be written about Hotmail or AOL. They could even be written about the various spam filter vendors and blocklists. Every company has their own way of doing things and their way reflects their underlying business philosophy.