PEmail Deliverability Glossary

PTR Record (Pointer Record / Reverse DNS)

A DNS record mapping an IP address back to a hostname (reverse DNS). Many receiving servers reject email from IPs without a matching PTR record.

A PTR record performs the reverse of an A record — it maps an IP address back to a domain name. This is called reverse DNS (rDNS).

Why PTR matters critically for email delivery:

Many receiving mail servers perform a PTR check on every inbound connection. They verify:

Does the sending IP have a PTR record?
Does that PTR record point to a hostname?
Does that hostname's A record point back to the sending IP? (Forward-confirmed reverse DNS)

If any step fails, the server may reject or score your message negatively.

Example of correct FCrDNS:

Sending IP: 198.51.100.15
PTR record: 198.51.100.15 → mail.yourdomain.com
A record: mail.yourdomain.com → 198.51.100.15 ✓

Setup: PTR records are managed by whoever owns the IP address — your hosting provider, cloud provider, or ESP. Unlike DNS records (which you control), PTR records must be set by your IP provider. Contact them directly to set this up.

Frequently Asked Questions

How do I check if my PTR record is set up correctly?

Use MXToolbox's Reverse Lookup tool (mxtoolbox.com/ReverseLookup.aspx) — enter your sending IP address to see what hostname it resolves to. Then verify that hostname resolves back to your IP with a forward DNS lookup (mxtoolbox.com/DNSLookup.aspx). Both directions must match for FCrDNS to pass. You can also use the Linux command 'dig -x [IP]' for reverse lookup and 'dig [hostname]' for forward lookup. If you're unsure which IP your emails are sent from, send a test email and check the 'Received' headers — the originating IP is listed there.

My hosting provider won't set a custom PTR record — what do I do?

If your current hosting provider doesn't allow custom PTR records (common with some shared hosting and cheaper VPS providers), you have a few options: upgrade to a plan that supports custom reverse DNS, migrate to a provider that allows it (AWS, DigitalOcean, Vultr, Linode, and most dedicated server providers support custom PTR), or use an ESP's sending infrastructure that already has proper PTR records configured. For most email senders, using a dedicated cold email ESP or warm-up tool that handles infrastructure setup is the easiest path — you avoid the PTR problem entirely by sending through their properly configured infrastructure.

Does every sending IP need its own PTR record?

Yes — each IP address in your sending pool should have its own PTR record that resolves to a relevant sending hostname, and that hostname's A record should resolve back to the same IP. If you're sending from multiple IPs (common with dedicated IP pools at higher volumes), you need PTR records configured for each one. The hostname format typically follows a pattern like: mail1.yourdomain.com, mail2.yourdomain.com, etc. Some ESPs that manage dedicated IP pools handle PTR configuration automatically — verify this when setting up dedicated IPs with any provider.

Related Terms

A Record

A DNS record that maps a domain name to an IPv4 address. A correctly configured A record is part of the complete DNS foundation required for email deliverability.

Forward DNS (DNS Lookup)

A standard DNS lookup that resolves a hostname to an IP address — a basic sanity check that receiving servers perform on every inbound SMTP connection.

Email Infrastructure

The complete technical stack for sending and receiving email — servers, IPs, DNS, authentication protocols, and monitoring tools.

Authentication (Email Authentication)

The set of technical protocols (SPF, DKIM, DMARC) that verify a sender's identity and prove an email genuinely originated from the claimed domain.

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