This is true for businesses that send out their own email, as well. There has been a lot of discussion about the value — or lack of — checking r DNS as part of the checks that mailbox providers perform routinely.Being pragmatic, your role is actually about getting your email to the inbox, so let’s focus on passing that test.[NOTE: ISIPP Surety Mail can set up your r DNS for you if you would rather not do it yourself.For more information about this service, contact us here.] What is r DNS?One of the first things that a responsible ESP must deal with, before starting to mail on behalf of their customers, is Reverse DNS (r DNS from now on). Note: This is the first in our series of tutorials on how to set up authentication mechanisms for your mail server, including r DNS, SPF, DKIM, and DMARC.
) that has been associated with a given IP address.Before we go into how to set up your r DNS, let’s have a brief discussion of how email receivers use it, at the other end, to identify who is sending them email.NOTE: The below discussion is highly technical, and you can skip it if you like, and go straight to the section ‘How to Configure r DNS‘.The process of r DNS delegation (we’ll define this further down) for IP version 4 was briefly defined in RFC-1033. You can also use (much more verbose) `nslookup` for this purpose, as follows: system_prompt$ nslookup 226.2. For IP version 6 (“IPv6″), the idea is similar although some lessons were learned in the process.
It uses a special type of DNS Resource Record called a “Domain Name Pointer”, or “PTR” which is defined in RFC-1035 for this purpose.
You may think of r DNS as a caller-id of sorts, helping the receiver know who is trying to send email.