How to check and verify PTR alignment?

You've set up a PTR record for your sending IP. Now how do you actually confirm it's working correctly? That's what PTR alignment checking is all about, and it's simpler than it sounds once you know what you're looking for.

A quick primer before the commands. A PTR record maps an IP address back to a hostname. For example, IP 192.0.2.1 might point to mail.tidalmail.com. That's the reverse direction. The forward direction is the normal one: a hostname like mail.tidalmail.com pointing to an IP. PTR alignment (also called FCrDNS, or Forward-Confirmed reverse DNS) means both directions agree. The IP points to the hostname, and the hostname points back to the same IP. When they match, receiving servers trust you more.

Step 1: Look up the PTR record for your sending IP

Open a terminal and run this command, replacing the IP with your actual sending IP:

dig -x 192.0.2.1

In the answer section, you're looking for a line that says PTR followed by a hostname. Something like mail.tidalmail.com. That's your PTR record. If nothing comes back, your PTR isn't set yet.

Step 2: Confirm the hostname points back to the same IP

Take that hostname and run a forward lookup:

dig A mail.tidalmail.com

The IP address in the result should match the IP you started with. If it does, you've got full PTR alignment. If it returns a different IP, or nothing at all, the alignment fails.

Step 3: Check IPv6 too (if you send over IPv6)

Still the same logic applies. Just pass the full IPv6 address to dig:

dig -x 2001:db8::1

Then do the forward check on whatever hostname it returns. IPv6 PTR mismatches are easy to overlook and surprisingly common.

Prefer a tool? Use MXToolbox

But if you'd rather skip the command line, MXToolbox has a Reverse Lookup tool that handles both steps for you. Paste your IP, and it shows the PTR record and whether the forward confirmation passes. DNS Checker has a PTR lookup as well, and it's useful for checking propagation across multiple resolvers at once.

What to do if alignment fails

If the PTR record is missing, contact your hosting provider or ISP and ask them to create a PTR record for your sending IP pointing to your mail hostname. If the hostname resolves to a different IP, check your A record. One of the two is misconfigured. After any change, wait for DNS propagation and re-run both lookups to confirm.

It's worth re-checking PTR alignment any time you change your sending IP, move to a new server, or update your DNS. It's one of those things that can quietly break in the background and affect how receiving servers score your reputation.

Not sure where to start or something's not adding up? Our SOS hotline is free and we'll help you trace the problem.