Email Snafu

How a Tracking Pixel can Break Your Email


Last Friday we sent out a carefully tested interactive email, only to find that when it hit inboxes there was a huge problem. This is pretty much an email marketer’s worst nightmare! We thought we’d write about it here so that it hopefully doesn’t happen to you.

The Email

The email we sent out can be viewed here. The idea was to send out our infographic from our industry survey with a few “hotspots” that would have additional content for curious readers. The hotspots work on hover for web or desktop clients, and on tap for mobile clients.

We tested the email in our system, as well as on a few phones so that we could play with the interactive features. Everything looked great!

What Went Wrong

Our ESP added a 1px tracking pixel to the email when it was sent out “for real.” This pixel wasn’t added to any of the testing emails, which is why we couldn’t see the problem. The email ended up looking like this on iPhone 5S, iOS9 on the final send:

Original Email


Buggy final send


The pixel, combined with a fluid container table which was set to “max-width: 600px;”, caused just enough extra space to trigger some kind of display bug in iOS. If the table had been set to “max-width: 602px;” or more, there would have been no issue. The same goes for the cellpadding=”0″ attribute, which would have saved our butts. You can check out the email code (and grab it to test the effects of the pixel for yourself) right here.

Lessons Learned

The main lesson we learned here is that a 1px tracking pixel can actually wreak quite a lot of havoc in a complex email! I would have never thought that something so tiny could have induced display issues like these.

What can be done about this in the future? If your ESP adds a tracking pixel to “test” sends, then you shouldn’t need to worry about this.

If not, one option is to add a fake tracking pixel where you know your ESP will add theirs. This will mimic the effects of a tracking pixel on your email. Another option would be to clone the campaign and do a “live send” to your testing system and phone to check if the added pixel will have an effect.

Email marketing is hard. We’ve all made mistakes or sent out broken campaigns. What unforeseen problems have you had? Let us know on Twitter or in the comments below!

3 thoughts on “How a Tracking Pixel can Break Your Email”

  1. At my current company we make “live tests” part of the QA process. ESPs can do some strange things with code, including tracking pixels, that can muck up the email. The live test is essentially performing the send, but to your test list so you get the message as your recipients eventually will.

    Marketing Cloud will allow you to do multiple sends from one email and hide tracking links and send data from reporting, and you can work around ESPs that don’t allow this through manual reporting.

  2. Kudos to you guys for owning the mistake (not sure that’s the right word), sharing the details and turning it into a learning opportunity for us all!

  3. Great post Geoff. I agree with Brent, thank you for sharing this and helping everyone learn from this. I’ve never run into this problem before because like Brandon, I use ExactTarget Marketing Cloud (regretfully sometimes). We always send live email tests to seed lists rather than using the native “send test” functions for a variety of reasons, one of which is indeed this pixel issue. Some other reasons people should steer away from those “test only” sends include testing unsubscribe, FTAF and managed preference links, viewing online version link and of course personalization. I don’t know about other ESPs, however in ExactTarget, the “test only” emails will not include personalization strings, so that alone makes it worth having a live seed list. Anyway, thanks again for sharing and look forward to reading more of your team’s posts. Cheers!

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