SUMMARY: if you cannot seem to hide the hostname of your mail exchanger on
outgoing email, it may be because you have an MX record that points to a
CNAME instead of an A record.
On my server, I've set up several domains, including "netmail.to". The
actual hostname is "server1.netmail.to". When I sent email, it was always
from "user@???", instead of the correct "user@???".
This can cause many problems, even though the mail gets through.
(In trying to figure out what was going wrong, I switched from sendmail to
exim, so this problem turned out to be a very good thing. But I digress...)
I created the proper exim rewriting rules, and exim in debug mode indicated
it was doing the correct thing. There was no mention of "server1" in the
envelope or mail headers. Yet when received at the other end, "server1" was
back in there...
I got suspicious of my ISP's DNS configuration, which had the "netmail.to"
MX record pointing to a CNAME "pop.netmail.to". They claimed repeatedly
that this was their normal practice and no one else had a problem. But they
were wrong. When I insisted they change the MX record to point to an A
record, all started working correctly.
My previous employer had the same problem and their support staff never
figured it out, and my current ISP has evidently set up dozens of client
servers in this way, so it's a common problem you may be called upon to fix.
Wayne Folta
wayne@???
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