On 16 Mar 2019, at 8:59, Johannes Bauer wrote:
[...]
You MTA is known under different names:
johannes-bauer.com mail is handled by 10 johannes-bauer.com.
spornkuller.de mail is handled by 10 spornkuller.de.
Is this a problem?
It should not be. There are no CNAMEs involved, so no room for obvious
failure modes.
In other words, should I refer to the MTA always
under the same name, i.e., have the MX record of johannes-bauer.com
point to spornkuller.de? If this is somehow an issue I definitely
overlooked it.
That really shouldn't matter. Just never point an MX at a name that is
resolved via a CNAME.
However, using multiple names for a mail server is generally pointless
beyond satisfying human urges. Some might call it "branding" or
"narcissism" or "nominalism."
It is simplest to just use one name for the server and have the PTR for
the IP and the MX for each domain it serves point to that name. In
Postfix that is set by smtp_helo_name, which defaults to $myhostname.
It does not advertise ESMTP (how the heck did you manage to
miss-configure it this much?):
| % nc spornkuller.de 25
| 220 Hi there
Ugh!
smtpd_banner = Hi there
My best guess is that I was testing something and had it
half-configured
or whatever. I'm fairly sure that it was previously disclosing full
version numbers
Which is really quite harmless.
and that's why I was poking around with that setting to
avoid it. Fixed and thanks for the pointer.
The text part of the connection greeting banner is not subject to any
formal requirements. There are recommendations in various RFCs but no
robust SMTP client cares what comes after the 220.
Is the banner however also used when Postfix connects to a different
MTA?
No. Again: that's smtp_helo_name (default: $myhostname)
--
Bill Cole
b...@scconsult.com or billc...@apache.org
(AKA @grumpybozo and many *@billmail.scconsult.com addresses)
Available For Hire: https://linkedin.com/in/billcole
