I have been trying to get Avast to work with Thunderbird, but so far no succes(I use Gmail).
Avast gave me a an error, saying that I need to disable SSL/TSL, which I did in Thunderbird.
I went to account settings and disabled SSL/TSL and still nothing.
I haven’t changed a thing in the Thunderbird settings, so I really have no idea what went wrong.
You need to set the incoming and outgoing security to none in thunderbird.
I forgot to turn off the security for the outgoing server -.-
It is all working now, thanks 
Your welcome