Can a PTR record have a different IP as the MX record?

Hello,

I hope someone can help...

I noticed that AOL does not allow emails without a reverse mapping in
the zone data.

My mail server is on a different IP (different physical location) from
my web site which emails to clients from it's own SMTP server.

Can I just insert a PTR record with the IP of SMTP server? Will that
work even though it is different than the IP of the MX?


Thank you in advance,
paul

Re: Can a PTR record have a different IP as the MX record?

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stile writes:

> Hello,
>
> I hope someone can help...
>
> I noticed that AOL does not allow emails without a reverse mapping in
> the zone data.
>
> My mail server is on a different IP (different physical location) from
> my web site which emails to clients from it's own SMTP server.
>
> Can I just insert a PTR record with the IP of SMTP server? Will that
> work even though it is different than the IP of the MX?

No.

The PTR record must point to a domain name with an A record (or AAAA, for
the pedantically-inclined) that has the same IP address referenced by the
PTR.



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Re: Can a PTR record have a different IP as the MX record?

Would this be valid?

www.example.com IN A xxx.xxx.xxx.10
smtp.example.com IN A xxx.xxx.xxx.20
20.xxx.xxx.xxx.in-addr.arpa IN PTR smtp.example.com.

When users on www.example.com get an email sent through
smtp.example.com, will that work?

Thank you so much,
paul

Re: Can a PTR record have a different IP as the MX record?

stile wrote:

> Would this be valid?
>
> www.example.com IN A xxx.xxx.xxx.10
> smtp.example.com IN A xxx.xxx.xxx.20
> 20.xxx.xxx.xxx.in-addr.arpa IN PTR smtp.example.com.
>
> When users on www.example.com get an email sent through
> smtp.example.com, will that work?
>
> Thank you so much,
> paul
>

Yes that is valid. This is what meant by matching forward-reverse
resolution.

Depending on what DNS service you are using, you would likely not need
to have the explicit definition you have or you would need to terminate
the string 20.xxx.xxx.xxx.in-addr.arpa with a period. i.e.
20.xxx.xxx.xxx.in-addr.arpa. IN PTR smtp.example.com.

AK

Re: Can a PTR record have a different IP as the MX record?

On 27 Oct 2005 14:59:10 -0700, "stile" wrote:

>Hello,
>
>I hope someone can help...
>
>I noticed that AOL does not allow emails without a reverse mapping in
>the zone data.
>
>My mail server is on a different IP (different physical location) from
>my web site which emails to clients from it's own SMTP server.
>
>Can I just insert a PTR record with the IP of SMTP server?

Here's what AOL says:

"AOL does require that all connecting Mail Transfer Agents have
established reverse DNS, regardless of whether it matches the domain.
Reverse DNS must be in the form of a fully-qualified domain name
Reverse DNS containing in-addr.arpa are not acceptable, as these are
merely placeholders for a valid PTR record. Reverse DNS consisting only
of IP addresses are also not acceptable, as they do not correctly
establish the relationship between domain and IP address."

That seems to say that the reverse and forward lookups don't have to
match up, but some place do require that.

> Will that
>work even though it is different than the IP of the MX?

The MX record has nothing to do with it. Sending servers don't have to
be MX servers.

Steve Baker

Re: Can a PTR record have a different IP as the MX record?

stile wrote:
> I noticed that AOL does not allow emails without a reverse mapping in
> the zone data.
>

It doesn't allow emails from hosts without a valid PTR record.

> My mail server is on a different IP (different physical location) from
> my web site which emails to clients from it's own SMTP server.
>

That doesn't matter. Whatever host is talking to AOL needs a valid PTR
record. If that host is your web server, then that host needs a valid
PTR record, perhaps:

smarty-foo.example.net. IN A 10.0.0.1
blurdybloop.example.net. IN A 10.0.0.2
www.example.net. IN CNAME smarty-foo.example.net.
smtp.example.net. IN CNAME blurdybloop.example.net.

....

1.0.0.10.in-addr.arpa. IN PTR smarty-foo.example.net
2.0.0.10.in-addr.arpa. IN PTR blurdybloop.example.net

If your webserver talks directly to AOL's incoming mailservers via
ESMTP, AOL will look for the PTR record for 10.0.0.1, and expect to be
able to resolve the result to that IP address.

> Can I just insert a PTR record with the IP of SMTP server? Will that
> work even though it is different than the IP of the MX?

No.

Dave.

Re: Can a PTR record have a different IP as the MX record?

Thanks everyone for your replies.

I ended up doing this:

www.example.com IN A xxx.xxx.xxx.10
smtp.example.com IN A xxx.xxx.xxx.20
20.xxx.xxx.xxx.in-addr.arpa IN PTR smtp.example.com.

sending emails from the www.example.com--->smtp.example.com--->AOL.com
now works.

Really appreciate the help!

-stile