PTR Records and Email: Why Reverse DNS Matters for Deliverability
Understand PTR records (reverse DNS) and why they matter for email deliverability. Learn how to check and configure PTR records for your sending IP.
When your email server connects to a receiving server, the receiver does a reverse DNS lookup on your sending IP address. If that lookup fails — or returns a suspicious result — your email is more likely to be rejected or filtered to spam.
PTR records (pointer records) are the DNS records that make reverse DNS work. If you manage your own email infrastructure or use a dedicated sending IP, PTR configuration is essential.
What Is a PTR Record?
Normal DNS maps a domain name to an IP address (forward DNS). A PTR record does the opposite — it maps an IP address to a domain name (reverse DNS).
When you send email from IP 198.51.100.25, the receiving server asks: "What domain does 198.51.100.25 belong to?" The answer comes from the PTR record.
Why Email Servers Check This
Legitimate email servers have PTR records that resolve to meaningful hostnames. Spammers often send from IP addresses with no PTR record, or with PTR records that point to generic ISP hostnames (like 198-51-100-25.dynamic.isp.net).
Checking PTR records helps receivers filter out:
- Compromised home computers and IoT devices sending spam
- Dynamic IP addresses that shouldn't be sending email
- Servers set up hastily by spammers without proper DNS
How PTR Records Affect Deliverability
Google's Requirements
Google explicitly requires PTR records for sending IPs. Their bulk sender requirements state that every IP sending email to Gmail must have a valid PTR record. The PTR hostname must resolve back to the sending IP (forward-confirmed reverse DNS).
What Providers Check
| Check | What It Means | Impact If Missing |
|---|---|---|
| PTR exists | The IP has a reverse DNS entry | Some providers reject outright |
| PTR is meaningful | Hostname isn't a generic dynamic IP pattern | Increases spam score |
| Forward-confirmed | PTR hostname resolves back to the same IP | Required by Google and many others |
Forward-Confirmed Reverse DNS (FCrDNS)
The gold standard is forward-confirmed reverse DNS:
- Reverse lookup:
198.51.100.25→mail.yourdomain.com(PTR record) - Forward lookup:
mail.yourdomain.com→198.51.100.25(A record)
Both directions must match. If your PTR says the IP is mail.yourdomain.com, but mail.yourdomain.com resolves to a different IP, the forward confirmation fails.
Do You Need to Configure PTR Records?
Using a Managed ESP (Most Common)
If you use an ESP like Mailchimp, SendGrid, Klaviyo, or Brevo, they handle PTR records for their sending infrastructure. You don't need to configure anything — the ESP maintains proper reverse DNS for their IP addresses.
This applies to both shared and dedicated IPs managed by the ESP.
Running Your Own Mail Server
If you operate your own email server (Postfix, Exchange on-premises, etc.), PTR configuration is your responsibility. Contact your hosting provider or ISP to set the PTR record for your server's IP address.
Using a Dedicated IP from Your ESP
Some ESPs let you set custom reverse DNS for dedicated IPs. This is recommended — having your PTR point to your own domain (like mail.yourdomain.com) rather than a generic ESP hostname strengthens your sending identity.
Check your email setup
Run a free deliverability check on your domain. Verify SPF, DKIM, DMARC, and MX records are correctly configured.
How to Check Your PTR Record
Find Your Sending IP
Before checking PTR, identify your sending IP:
- Check your ESP dashboard for the sending IP
- Send an email and examine the
Receivedheaders - Ask your ESP or hosting provider
Check Reverse DNS
Use command-line tools or online DNS lookup services:
Command line:
nslookup -type=ptr 198.51.100.25
or
dig -x 198.51.100.25
The result should show a meaningful hostname that relates to your domain or your ESP's infrastructure.
Verify Forward Confirmation
After finding the PTR hostname, confirm it resolves back:
nslookup mail.yourdomain.com
The returned IP should match your sending IP.
How to Set Up a PTR Record
PTR records are different from other DNS records — you can't add them through your normal DNS provider. PTR records are managed by whoever controls the IP address block.
Identify who controls your IP
This is usually your hosting provider, ISP, or cloud provider (AWS, GCP, Azure). They manage the reverse DNS zone for their IP ranges.
Request a PTR record
Contact your provider and request that your IP's PTR record be set to your chosen hostname (e.g., mail.yourdomain.com).
Cloud providers often have self-service options:
- AWS: Set reverse DNS through the EC2 console
- GCP: Configure through the networking settings
- Azure: Available in the public IP address settings
Create the matching A record
Add an A record for the PTR hostname pointing to your IP:
mail.yourdomain.com → 198.51.100.25
This creates the forward-confirmed reverse DNS.
Verify both directions
After propagation, verify that reverse lookup returns your hostname and forward lookup returns your IP.
Common PTR Issues
No PTR Record
The IP has no reverse DNS entry at all. This happens with newly provisioned cloud servers or when the hosting provider hasn't configured reverse DNS.
Impact: Gmail and some other providers will reject or filter email from IPs without PTR records.
Generic Hostname
The PTR points to something like ec2-198-51-100-25.compute-1.amazonaws.com or 198-51-100-25.your-isp.net. This isn't wrong, but it doesn't identify you as a legitimate email sender.
Impact: Increases spam score. Not a hard rejection trigger, but contributes to overall filtering decisions.
Mismatched Forward/Reverse
PTR says mail.yourdomain.com but that hostname resolves to a different IP. This breaks forward confirmation.
Impact: Google treats this as a PTR failure. Other providers may flag it.
PTR Points to Unrelated Domain
If your PTR record points to a domain you don't control or that doesn't relate to your sending domain, it looks suspicious.
Impact: Raises red flags. Receiving servers may view this as a compromised or misconfigured server.
PTR for IPv6
If you send email over IPv6 (increasingly common), IPv6 addresses also need PTR records. The same principles apply — reverse lookup should return a meaningful hostname, and forward lookup should confirm the address.
IPv6 PTR records are longer to configure (due to the address format) but function identically to IPv4 PTR records.