# PTR Records and Reverse DNS

Most marketers are familiar with DNS names that resolve to an IP address.

For instance:

extmta2-new\.americanexpress.com resolves to 148.173.96.85 as you can see here:

{% embed url="<https://www.whatsmydns.net/#A/extmta2-new.americanexpress.com>" %}

<figure><img src="https://2024949584-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FHNgw7cfnOYHQr0B6GDXr%2Fuploads%2FiwFvrXaYzyUXYROloo7D%2FScreenshot%202024-01-09%20at%2010.38.47%E2%80%AFPM.png?alt=media&#x26;token=a70bd1a9-a01e-4184-98a7-1b77d5c34e3a" alt=""><figcaption></figcaption></figure>

This is known as a DNS A record, often the type of record you create in your DNS hosting provider when you want to add a domain to your website. In the email space, this is sometimes known as the "forward ".&#x20;

As the postmaster of an MTA,  there's another type of record you'll need to familiarize yourself with that's just as important as the A record in the email space; it's called the PTR, also known as "reverse" DNS.&#x20;

In our example above, we see that extmta2-new\.americanexpress.com has an A record that resolves to 148.173.96.85, but when you do a PTR lookup, you'll see 148.173.96.85 also has a DNS record, and that it resolves to extmta2-new\.americanexpress.com.&#x20;

{% embed url="<https://www.whatsmydns.net/#PTR/148.173.96.85>" %}

<figure><img src="https://2024949584-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FHNgw7cfnOYHQr0B6GDXr%2Fuploads%2FMCHPttGFAld1AFSOuAmC%2FScreenshot%202024-01-09%20at%2010.37.05%E2%80%AFPM.png?alt=media&#x26;token=ac49865b-def3-4592-b64d-8218fd72364a" alt=""><figcaption></figcaption></figure>

The A record for extmta2-new\.americanexpress.com is 148.173.96.85 and the PTR record for 148.173.96.85 is extmta2-new\.americanexpress.com.

They match.&#x20;

{% hint style="info" %}
You'll occasionally see the acronym FCrDNS used to describe the necessity of the PTR  record matching the A record, which stands for "Forward-Confirmed Reverse DNS."
{% endhint %}

Here's why:

<figure><img src="https://2024949584-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FHNgw7cfnOYHQr0B6GDXr%2Fuploads%2Fb78Dp2Z9hfTQKjfUNWbW%2FScreenshot%202024-01-09%20at%208.21.25%E2%80%AFPM.png?alt=media&#x26;token=379a7676-3815-44b4-83b1-11d6279e83fb" alt=""><figcaption></figcaption></figure>

{% hint style="info" %}
If you don't have a PTR record for your sending IP address, and your PTR and A record of your sending domain don't match, Gmail will reject your mail.&#x20;
{% endhint %}

<div align="left"><figure><img src="https://2024949584-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FHNgw7cfnOYHQr0B6GDXr%2Fuploads%2FHgPGBq6gasVdTpcvF0Aj%2FScreenshot%202024-01-10%20at%202.58.52%E2%80%AFPM.png?alt=media&#x26;token=5387015c-7233-4a7d-b92d-0d6132582be0" alt="" width="563"><figcaption></figcaption></figure></div>

It's important to create your DNS records before you install Velocity MTA, add your IP addresses, and send your first test message.&#x20;

When Gmail rejects your message for reasons such as bad or missing DNS records or authentication failures, if you're a first-time sender, this erroneous result may get cached, preventing you from successfully delivering a message for at least 24 hours after you've fixed the problem.&#x20;

Don't risk it.&#x20;

{% hint style="info" %}
The PTR record can only be set by the owner of the IP address, which will likely be your VPS provider.
{% endhint %}

You can't set the PTR record in Cloudflare, Namecheap, GoDaddy, or anywhere you normally configure your DNS A record.

Some hosting providers allow you to configure your PTR record right in the control panel, but it's not uncommon that it can only be done by opening a ticket. This is the case with Racknerd.

See the next section [Sending Domain and PTR must match](https://docs.emaildelivery.com/docs/what-you-need-to-know-before-you-install-velocity-mta/sending-domain-and-ptr-must-match) for the recommended DNS configuration.&#x20;