I use gmail.

When I reply to a thread using Thunderbird, the response never
shows up, but, if I include the email of the person who wrote
the thread I am responding to, that person gets the email.
                                               
On the other hand, if I log in to my gmail account, the
I can post a response, that that response appears as a new,
top-level discussion thread.                   
                                               
How do I response to a message in a thread using Thunderbird
and have the users@lists.fedoraproject.org accept it?

Thanks                       
Richard