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Spamhaus reminds us to keep our lists clean

A few days ago The Spamhaus Project published a response to some observations and assumptions made by large ESPs over what they felt were new ways of handling spam traps. Right around the holiday, big senders noticed that transactional emails were causing their IPs to get listed with Spamhaus.

What’s the Spamhaus Project? #

For those unfamiliar, Spamhaus is a very well respected and far-reaching Spam monitoring organization. They monitor IPs and domains for sending spam and provide this data to ISPs as well as law enforcement. Years ago when we still ran Newsberry we got listed once. Our emails started bouncing with Gmail, Hotmail, and almost all other senders (large and small). It was a terrible situation, one I hope never to have to deal with again. Spamhaus is always right, though. Our customer wasn’t behaving and we got blocked for it.

How Spamhaus catches bad senders #

Spamhaus uses spam traps as one of it’s ways to catch any sender who doesn’t practice good list hygiene. A spam trap is an email address that exists for the sole purpose of catching spammers. It has either been retired by someone, or it can be a commonly mistyped domain ( that has been picked up by spam services like Spamhaus. You should strive for never having one of these in your list because they never asked to hear from you. If you send to many spam traps, there is something really wrong with your acquisition practices, or you’re not properly retiring emails.

How Postmark ensures good list hygiene #

When we started running Postmark, we always knew that we would be strict with our handling of bounces and spam complaints. There are some mixed opinions on how many times you should let an email hard bounce before you deactivate it. We always took the stance that if an email hard bounced once, we don’t send to it again. Postmark will automatically disable the email and we won’t let you send to it again, unless you manually intervene.

Of course there can be false positives, but for the most part, ISPs and mail servers respond properly with hard bounces. If an email doesn’t exist, why send to it two more times? In the three years of running Postmark, we have often had to explain or defend ourselves to customers why we do it this way. We know it can be annoying reactivating false positives but it pays off in the long run.

In marketing emails there are tons of best practices on how to keep your list clean of spam traps. The trend is quickly moving towards measuring engagement. This means keeping track of how users interact with your emails and continuing to email those that actually open or click links in your email. In transactional email there are far fewer options for those kinds of measures. So what you HAVE to pay attention to is bounces and spam complaints. If you’re sending a transactional email to an email that is bouncing, disable it.

Summary #

It’s really enlightening to read the response from Spamhaus. All of the senders they listed were sending transactional email to spam traps, over and over. Even more crazy is that these email traps actually responded with a bounce, and still they were never looking at the SMTP responses or engagement. It really is fantastic proof that you should pay very close attention to all of your mailings. And it also shows how important it is to separate marketing and transactional email. You’ll see even Spamhaus reacts differently to spam traps hit by marketing emails vs. transactional email. They are more lenient to transactional mailings because they understand that typos happen.

Last thing I want to mention is that as a Postmark user, you can and should fix these issues. Use our Bounces API to keep track of bounces. Use our web hooks to notify customers in your own applications to fix their typos so they receive your email. Transactional emails are your lifeblood, let us help you get them where they need to go.

Natalie Nagele

Natalie Nagele

Wildbit CEO. Love my kids, travel adventures and parties.