Hai gcacciola,
I had the same problem, also with the combination of Postie and Email Subscribers.
Before I updated WordPress to the latest version (4.7.2) everything was working fine.
I have been working on this for several days, testing all different kinds of settings, versions of the 2 plugins. No luck.
Until today. I found out another plugin caused the probleym (Ryo category visibility)
After switching this plugin off everythins is working again.
Fot the Ryo plugin I found a good alternative. (Ultimate Category Excluder)
