Having just done a reinstall of avast for Avast Free 18.2.2328, I wanted to link (sign in) my new installation to my.avast.com account.
When entering my valid email address (which has an underscore _ character in it the process reports it as an invalid email.
I can logon directly to my.avast.com (or if going directly to the forums) with that email, it is valid. What I don’t know is which side is responsible for reporting the underscore _ character as being an invalid email, the avast free program (never had this before) or is it my.avast.com.
Wherever the problem lies this needs to be resolved may email providers/servers accept the underscore _ character.
Of course I can simply not bother connecting this installation to my.avast.com, my main point is this could also be impacting on other users.