Rumpel--I did understand most of what you said, and knew that Avast wanted me to change the settings. However, what I DIDN'T understand, was that Avast was going to do the SSL part FOR me. I understand, now. Thank you.
Pondus & Logos--After reading and re-reading everything (several times through the whole thread), I finally DID understand that you gave me the answer in your first post, Logos. I'm sorry I didn't catch it, then.
I have now done that, and I have tested, and my gmail DOES come in just as it should, with no pop-up from Avast.
So...my question has been answered and my problem solved, and nothing about Avast needs to be changed, obviously!
Please forgive me for not understanding in the beginning. It just took some people coming at the thing from different directions, I guess, for me to see what I was missing.
Thanks to ALL of you, and this thread can now be marked SOLVED, or whatever it is that you need to do.