Reverse DNS and mail

[Mike DiChiappari]

> 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 foo.com or bar.com, depending on
who is sending email (we host both foo.com and bar.com).  So wouldn't a
recipient mail client want foo.com's IP address to resolve to foo.com and
bar.com's IP address to resolve to bar.com?  Conversely, wouldn't an email
client that does reverse DNS reject email where foo.com's IP address
resolves as bar.com.

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

> 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?

Mike