Google DFP ads in email behaving strangely

Question

I am trying out serving DFP ads in email. I'm following the guidelines here.

• I have an ad unit set up just for email
• I have a line item targeting that ad unit with just an image creative
• The line item doesn't have any targeting restrictions or anything like that

The ad will show up in the email, at least the first time. The strange thing that I'm seeing is, after the first click, clicking on the ad again will often bring me to a blank page rather than the click-through page of the creative. Also, when I reopen the message, occasionally the image will not load. The code in the email looks like this:

<a href="https://pubads.g.doubleclick.net/gampad/jump?iu=/{my_pub_id}/300x250_email&amp;sz=300x250&amp;c={cachebuster}&amp;tile=1">
<img src="https://pubads.g.doubleclick.net/gampad/ad?iu=/{my_pub_id}/300x250_email&amp;sz=300x250&amp;c={cachebuster}&amp;tile=1" />
</a>

Answer 1

We've solved this by turning off cookies in the standard tag using the co= option; adding co=1 to the tag.

<a href="https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/{my_pub_id}/300x250_email&amp;sz=300x250&amp;c={cachebuster}&amp;tile=1">
<img src="https://pubads.g.doubleclick.net/gampad/ad?co=1&iu=/{my_pub_id}/300x250_email&amp;sz=300x250&amp;c={cachebuster}&amp;tile=1" />
</a>

The only problem (for us) that this creates is that we're unable to serve 3rd party tags, even ones that resolve directly to .gifs, using the standard tag.