Here's our documentation about tagging an email campaign: Marketing campaigns.
For your information, the opening of e-mail campaigns is measured using an AT Internet pixel. This tag is in the following format:
<img width='1' height='1' alt='' src='http://logxxxx.xxxx/hit.xiti?s=xxxx&xto=A-B-C-D-E-F-G&type=email&' >
In addition, clicks on your campaign links are measured using link tagging. To set up such a tag, two configurations are possible:
The direct method
Use the direct method by adding the parameter xtor to your url, taking care to respect this format: