Anyone else have trouble with Apple Mail threading this list?

I use Apple Mail, and subscribe to many lists but PHP-General is the only one I have this problem with. People tell me that my replies are not properly threaded to the original post. When I hit Reply or Reply All in Mail, it wants to reply directly to the poster, and only CC's the list. So I drag the CC address up to the To field and delete the poster's address. Seems like the best I can do, but it creates this problem people have reported. Do I just totally suck, or is there a more reasonable explanation?