We currently have email opens working pretty well, we have an image in place that calls our adobe endpoint and passes variables, both props and evars. I was thinking though, what's the purpose of using an evar in an email open, especially when not all email clients don't support cookies (I'm guessing browser based clients may support cookies). If a true session was being set with a visitorID and all, I could see the point of having a session variable like an evar. Is there something I'm missing?
Looking through my clickstream data it seems that some email packages do support cookies, but not all do. I've run a test by setting the vid to a unique id and that seemed to track nicely in the clickstream and it keeps my visits (20 minute increments) together and it keeps my unique visitor proper. Plus I'd be able to easily track usage across devices, which would help answer the question of how many times to people use both phone and desktop for email (or at least multiple devices).
Interesting, but this would mean we'd need to pass the vid on each request, correct? We have something that we could use, but we're not using it yet (I inherited this application and I'm busy trying to undo several knots).