I'm facing the same issue, actually. I'd like to run email performance reports by country - as in country that sent the email, not country where the lead is.
All the filters I find are for the database, but not for the users. I was expecting to be able to use tags (like author or region) or email addresses to generate these reports, but they're not available anywhere.
Another solution to this would be to be able to filter by the email name. We have a naming convention by which each team use their country code at the front of the emails they send. But this is also not possible.
Have anybody managed to achieve a similar thing?
Cheers!