>> If I emailed directly to the account it works, if I do it via php >> mail, it fails. > > Have you confirmed that the gmail account is in fact receiving the > emails from php? Yes, of course. And if I press Reply from that account and send, then that letter goes to the right place. I tried this using two different gmail accounts--for both the auto response works for "direct" emails but fails for php. For both, however, the php-generated email gets to the right place and the Reply function works as expected. Thanks.