Thanks to all who have tried to help me so far. I'm sorry to be such a pest. I've tried a number of things and still can't get it.
Management wants email to user@ <a non-existent machine> .arlut.utexas.edu will be treated as though it had been addressed to u...@arlut.utexas.edu (sendmail can do this.) (I'd like to stop this practice, but, oh, well.) Is this much set up correctly? relay_recipient_maps = regexp:/etc/postfix/pfrecipient_canonical This file looks like this for the user schumi /^schumi@.*\.arlut\.utexas\.edu$/ sch...@arlut.utexas.edu I can send mail to schumi, schumi@correctmachine, and my backup mail server delivers the mail like I want it to. My relay_recipient_maps is such that I do match all possible subdomains. I don't get "recipient unknown" so it seems that much is correct. Mail to schumi@nonexistentmachine gets shoved to the primary internet connection. I can tell from the headers in the msg. So this mail server isn't doing this "fail-over" like management wants. I've read and re-read the addressing READMEs online. Is this "failover" from a non-existent, non-DNS MX, non-transport_maps machine to the right machine (see ns8,vme below) possible? The DNS MX lists only the primary and backup mail gateways (they don't do final delivery). There is a short list of machines which do take final delivery but none are in DNS MX records. These are listed in the transport_maps. Here's the transport_maps file used in the tests. ns8.arlut.utexas.edu smtp:[ns8.arlut.utexas.edu] vme.arlut.utexas.edu smtp:[vme.arlut.utexas.edu] I've tried adding .arlut.utexas.edu : But that will involve the primary mail servers (again, from the msg headers). For reference, schumi's alias looks like this: virtual_alias_maps = hash:/etc/postfix/pfmalias schumi sch...@vme.arlut.utexas.edu, sch...@ns8.arlut.utexas.edu j.