Reverse DNS and mail

User, Public public at
Thu Jan 8 18:54:39 UTC 2004

Hi Mike,
When a mail is sent, the sending server looks for an MX record for the
destination domain in DNS, and will open a connection to that IP address
to send the mail.  It is up to the receiving server to allow reception
of that mail depending if it is configured to receive mail for that
domain.  You can have hundreds, or even thousands, of domains configured
to be received on one mail server, with one IP address.  Each domain has
an MX record pointing to the same single address. =20

I think you are getting confused between mail clients/servers, and
forward/reverse DNS. =20


Christopher P. Jenkins, Senior Consultant

Concordant, Inc.

P:  508-820-3080

F:  508-820-4367

C:  508-241-7415

E:  chris.jenkins at

-----Original Message-----
From: bind-users-bounce at [mailto:bind-users-bounce at] On
Behalf Of Mike DiChiappari
Sent: Wednesday, January 07, 2004 11:09 PM
To: comp-protocols-dns-bind at
Subject: Re: Reverse DNS and mail

> There is no requirements that the mailserver has several FQDN, it's
> better to have each domain have an MX record to
> the "one-and-only" real mailserver

Yes, but our mail server could appear as or, depending
who is sending email (we host both and  So wouldn't a
recipient mail client want's IP address to resolve to
and's IP address to resolve to  Conversely, wouldn't an
client that does reverse DNS reject email where's IP address
resolves as

Another way to ask this is that if and have the same IP,
does one guarantee that upon reverse DNS lookup that joe at's IP
address resolve to  Maybe DNS will return

> Same goes with the nameservers for the zones, there is no
> point in faking separate names of the nameservers just to
> have them coincidence with the domain itself. In fact it's
> far less work to have fewer glue-records to keep up to date.

Won't email appear to come from the same domain then?


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