F21: Thunderbird insists on calling Fedora list messages junk!

[William]

Good afternoon,

Most messages received from this fedora list are labelled junk by 
Thunderbird.  This is even though I whitelisted "From" = 
"users-request at lists.fedoraproject.org".  Actually, I have this problem 
both in my Fedora-21 and my windows-7 systems.  Any ideas? Surely 
messages from this list are not junk!

thanks,
Bill.