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Exchange 2003 issue. Email bounces back when trying to send an email

Posted on 2007-07-26
Medium Priority
Last Modified: 2011-09-20
we are trying t send an email to domain abc.com but the email bounces back.
Their IT dept sent us the following reply. What exactly do we need to do ?


...Their mail server is failing our DNS verification test.  Their outbound mail server is  That address maps back to the name llshost8510.domain.com, but that name is not in the DNS.  They need to fix their DNS.

Here is an excerpt from a web page still under construction which explains the problem in more detail.  The text is still rough, but it gets the point across.

    Our servers perform a simple DNS verification on the IP address of
    each inbound SMTP connection. A reverse lookup is performed on the
    address to get its name, and that name is then looked up to get an
    address. If the two addresses don't match, or if either of the DNS
    queries fails, then this is considered a suspicious condition and the
    sending host is allowed to send us only one recipient per hour.

    In general, we do not grant exceptions to this rule. A DNS
    verification failure almost always indicates an error in your DNS
    configuration, which needs to be fixed. If you can demonstrate that
    your DNS is correct and that some other factor is leading to a false
    positive under this rule then we can exempt your server.

Question by:c_hockland
  • 2

Assisted Solution

thenone earned 600 total points
ID: 19578445
Does your mx record have a ptr?

Expert Comment

ID: 19578447
Point to return.

Author Comment

ID: 19578475
On the external DNS my MX record doesnt have PTR.
On the internal DNS i think it does.
So..do i need PTR (Reverse in Linux) on both external and Internal DNS ??
Thanks both of you in advance.

LVL 104

Accepted Solution

Sembee earned 1400 total points
ID: 19578485
Do you send email directly or via your ISPs SMTP Server?
If you send email directly then you need to ensure that you DNS is configured correctly.
Put your domain in to dnsreport.com and see if it flags any errors in the mail server section.

The message that you have received looks like it is doing a reverse lookup check, so I suspect that you either don't have one, it is invalid or it doesn't match what the server is announcing itself as.



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