>Subject is not the best thing to use for sorting the messages into >separate folders. You should use the List-Id: header. If my email client allowed me to sort on random headers I'd certainly do that. Alas, it's an imperfect world and what's correct seldom coincides with what's practical. In any case, the problem is not entirely with my email client. My spam filter is also involved in the problem and it doesn't know anything about "optional" headers. The only rules I can set there are based on the "standard" from, to, and subject headers. As for sorting based on the To: field, I already do this. If it was sufficient, well, I wouldn't have made the original request. No solution involving headers is going to catch off-list replies and these happen frequently given that the list messages use the sender's email address as the Reply-To header. If it's a religious issue then there's little point in discussing it. I'm sure the list owners have their reasons for wanting things a certain way.