SUMMARY

This article explains PTR records and how to configure them.

DETAIL

A Reverse DNS lookup is used by remote hosts to determine who 'owns' an IP address. For this to occur the 'owner' of the IP address must have registered a PTR record for the IP address.       

Many mail servers will perform a reverse DNS lookup on the IP address that is attempting to connect to them. Therefore the mail server needs to have a PTR record associated with the IP address that it uses to communicate with other servers.

The 'owner' of the IP address is the last host that responded to the DNS query. It is this host that needs to be reconfigured to either pass on the request for the PTR record or respond to the PTR request.

To create a PTR record requires access to the server that holds the DNS records.  More information on this can be found here: http://www.mailenable.com/kb/Content/Article.asp?ID=me020115

Otherwise, the owner (usually your ISP) will need to create the PTR record on your behalf.

MORE INFORMATION

How to set up PTR records under Microsoft's DNS Server: http://www.mailenable.com/kb/Content/Article.asp?ID=me020115

PTR record exists but the mail server is unable to receive mail from some domains: http://www.mailenable.com/kb/Content/Article.asp?ID=me020180

Unable to send email to some domains, such as Hotmail, Yahoo, etc.: http://www.mailenable.com/kb/Content/Article.asp?ID=me020003