Reverse DNS

By tzutzasialbu ·
Hi folks,

Lately, some users are getting this message error when sending emails to specific addresses.

5.5.0 smtp;550-Reverse DNS is missing or incorrect for the sending machine.

I know it's related to rDNS but I don't know how to setup rDNS for our email server.

Any help would be appreciated.

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Most likely your ISP

by Churdoo In reply to Reverse DNS

Reverse DNS zones are managed much like forward DNS zones, except they are managed by blocks of IP addresses. Most likely, your ISP (or even their ISP) manages the reverse DNS zone that contains your IP(s).

Go to and do a Whois search of your mail server's IP addy. This should lead you to who is managing the reverse DNS zone which contains your IP.

Next, go to your email server and figure out what its HELO/EHLO name is (in Exchange, this is located in ESM in the properties of the SMTP virtual server / Delivery / Advanced / "Fully qualified domain name")

Contact the DNS zone manager of your IP block that you found at and ask then to create a PTR record for your mail server's IP with the FQDN of your mail server.

Oh and by the way, is a great site for DNS tools and info.

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