After reading more, I think I had this feature a bit wrong. Replies aren't posted to tickets based on the email address, but rather on the, well, somehow the email knows which ticket to update. I found one forum that said I had to have the ticket number, in brackets, in the subject line of the notification email; I did that, but that didn't help anything. I guess my question has turned into:Why can't tickets be updated via email? Responses just disappear into nowhere. I'm starting to suspect my email setup, but I've selected tickets+admin@domain.com as the default system email, then set the notification email to use the system default. Yet, notifications come from tickets@domain.com, not tickets+admin@domain.com.