Reverse DNS and mail

[Len Conrad]

> > 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

"appear" where, specifically?

PTR?  HELO hostname?  SMTP greeting?   MAIL FROM:?

>, 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?

Repeating from my earler msg in this thread:

"Note that the (virtual) envelope/recipient domains of the traffic allowed
by the MTA's policies are not a consideration in the above settings (the
ESD/ERD don't have to match the above label.domain.tld)."

>   Conversely, wouldn't an email
>client that does reverse DNS reject email where foo.com's IP address
>resolves as bar.com.

ditto

>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?

it doesn't matter.

I suggest that you implement my DNS/SMTP advice and report back if you have 
problems delivering mail.

Len


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