tmda not automatically adding confirmation addresses to whitelist

So, I've setup TMDA to add e-mail addresses to the whitelist 
automatically.  This works fine when i use `tmda-process -i' and tell 
TMDA what addresses to whitelist (press the 'w' key when looking at a 
message).

But, I can't get TMDA to automatically add e-mail addresses to the 
whitelist from people send in a reply to the the challenge/response 
message that is sent out.

What am I missing?

Thanks.

Richard Schilling