Exclusion for Calibre in antivirus program

I have not been able to send any books to my kindle from calibre via email. I used to be successful via Gmail. I have followed all the instructions on the forum, including opening a GMX account. Still no luck. If I make an exclusion for Calibre for my antivirus software, Kaspersky, how do I do that? I'm hoping this is the issue? Otherwise, I'm at a complete loss. Thanks for the help!

ETA: I'm looking under the "Applications Activity" in Kaspersky and it says Calibre is "trusted" and has no restrictions. Is there somewhere else I need to be looking?

I also just tried to send a book with my antivirus and firewall disabled. Still didn't work, so now I'm wondering if something else is the problem?