We are seeing spikes to web visits in GA that correspond to days we send nurture emails via Marketo. Appear in GA with campaign source and medium are "zbexfgb.dbz / email".
Suggestion on how to address?
I've updated the Bot Activity setting in Marketo and reached out to Marketo support.
I would try to figure out which specific email domains have email scanning services on their end. I would try to figure this out by using Marketo, and seeing if you notice that people at a specific email domain click on multiple links in your emails within a short amount of time (e.g., 2 minutes or so). Try to understand who in your database poses specific bot activity. In regards to Google Analytics, I wouldn't know. Hopefully Marketo support would be able to help you with this.
All the best,