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What rDNS and PTR records are
Normal DNS turns a name into an IP address. Reverse DNS does the opposite: given an IP, it returns a hostname, using a PTR record. When your server connects to deliver mail, the receiver looks up the PTR for your IP. If there isn’t one, or it is a generic name like a string of numbers at your hosting company, the connection looks like it could be coming from a compromised home computer.
Receivers commonly check forward-confirmed reverse DNS: the IP resolves to a hostname, and that hostname resolves back to the same IP. Many also compare it with the name your server gives in its HELO or EHLO greeting.
Warning signs
- Rejections mentioning reverse DNS, PTR or “no hostname”.
- Your IP resolves to a generic hosting name.
- The PTR hostname doesn’t resolve back to the IP.
- Your server’s HELO name differs from its PTR.
- IPv6 mail fails while IPv4 works, often because the IPv6 address has no PTR.
Who controls the PTR record
Unlike your normal DNS, PTR records are controlled by whoever owns the IP address block, usually your hosting or cloud provider. Some let you set it in a control panel; others need a support request; a few don’t allow it on certain plans. We check this before a mail server is built, because a provider that won’t set reverse DNS isn’t suitable for sending.
On cloud platforms and shared sending services, the provider manages reverse DNS for its own IPs, so there is usually nothing for you to set. rDNS work matters when you have your own servers or dedicated IPs on a VPS or dedicated host.
What’s included
- A hostname scheme for your sending IPs, such as mail1 and mail2 on a sending subdomain.
- A records (and AAAA for IPv6) for each hostname.
- PTR records set through the provider’s panel or support.
- The MTA’s HELO name configured to match.
- Verification in both directions, for IPv4 and IPv6.
- Documentation mapping every IP to its hostname.
How we deliver it
- List all sending IPs, including IPv6 addresses the server may use without you realising.
- Agree hostnames and publish forward records.
- Set or request PTR records with your provider.
- Update the MTA configuration so the HELO name matches.
- Verify with lookups from outside your network and with test sends.
- Disable IPv6 sending temporarily if a provider can’t set its PTR, rather than send from an unverified address.
Where you have many IPs, we script the checks so every address is verified the same way and the results are recorded in the documentation.
Where rDNS fits
rDNS is a baseline trust signal. On its own it won’t get mail to the inbox, but without it much mail won’t be accepted at all. It sits alongside DNS configuration and email authentication, and matters most on dedicated SMTP where the IP is yours.
As with every part of sending infrastructure, it supports permission-based mail. It isn’t a way to make unsolicited mail look trustworthy.
Receivers also look at the hostname itself. A clear name on a sending subdomain signals a deliberately configured mail server. A generic name containing the IP address, or words that suggest a home connection, can count against you with some filters. Choosing a consistent naming scheme at the start also makes logs and monitoring easier to read later.
What affects timeline and cost
- Number of IPs, including IPv6.
- Your provider’s process and response time for PTR changes.
- Whether the MTA configuration also needs updating.
Common mistakes
Setting a PTR to a hostname that has no matching A record. Using the bare domain name as every IP’s hostname. Forgetting IPv6. Leaving the MTA announcing a default hostname like localhost. Assuming the hosting company set it up.
Browse all email infrastructure services, read the guide, or contact us.
Frequently asked questions
Can I set a PTR record in my domain’s DNS?
No. PTR records belong to the owner of the IP address, usually your hosting provider. We work with them to set it.
Does every sending IP need its own hostname?
It’s the clearest approach, and it makes logs, monitoring and troubleshooting much easier.
Why does my IPv6 mail fail but IPv4 works?
Very often the IPv6 address has no PTR record. Receivers can be stricter over IPv6, so it needs the same care.
Does the PTR hostname have to match my From domain?
No. It should be a real hostname that resolves back to the IP and matches your HELO name. It can be on a sending subdomain.
How long does a PTR change take?
Setting it can be instant in a control panel or take a support ticket, depending on the provider. After that, it follows the record’s TTL like any DNS change.
Talk to us about rdns (ptr) setup
Reverse DNS matched to your sending hostname — a basic trust signal every filter checks.