Donaldson R F
Email & SMTP
Configure Reverse DNS / PTR
Set up a matching PTR record for your mail server's IP so it stops looking suspicious to receiving servers.
The Problem
Missing or mismatched reverse DNS is one of the most common, least obvious reasons a dedicated mail-sending IP gets flagged or rejected outright by picky mail servers.
About this problem
Forward DNS (your domain pointing to an IP) and reverse DNS (that IP pointing back to a hostname) are separate systems, and mail servers increasingly check that they match — a mismatch or missing PTR record is one of the most common, least visible reasons a dedicated sending IP gets rejected or heavily filtered by strict mail servers.
This matters most for anyone running their own mail server rather than using a managed email service, since managed providers typically handle PTR records for you already.
What's Included
- Checking current PTR record (if any) against your sending IP
- Working with your hosting/VPS provider to set the correct PTR value (most require this from their side)
- Verifying forward-confirmed reverse DNS (FCrDNS) matches
- Confirming the fix with a live test send
What's NOT Included
- Hosts/providers that don't allow custom PTR records at all (some budget VPS providers don't)
- IPv6 PTR setup unless specifically requested
- Dedicated IP acquisition — that's between you and your host
How It Works
- Check the current PTR record (if any) for the sending IP address.
- Compare it against the hostname the mail server actually identifies itself as during the SMTP handshake.
- Work with the hosting or VPS provider to set the correct PTR value, since most require this to be configured on their end.
- Verify forward-confirmed reverse DNS (FCrDNS) — that the PTR hostname also resolves back to the same IP.
- Send a live test email and check the receiving server doesn't flag a PTR mismatch.
In practice: you buy the service, send over whatever access or details the job needs, I investigate and do the work, and you confirm it's resolved before we call it done.
Frequently Asked Questions
- What is a PTR record and why does it matter for email?
- A PTR record maps an IP address back to a hostname — the reverse of normal DNS. Many mail servers check that this matches what your server claims to be, and reject or filter mail more aggressively if it doesn't.
- Can I set up my own PTR record?
- Usually not directly — PTR records for an IP are controlled by whoever owns that IP block, typically your hosting or VPS provider, so it has to be requested through them.
- Why does my VPS provider need to set this, not me?
- PTR records live in a special reverse DNS zone tied to IP ownership, which is managed by whoever allocated that IP range — almost always your hosting provider, not your domain's DNS.
- What happens if I don't have a PTR record set up?
- Many strict mail servers will reject or heavily spam-filter mail from an IP with no reverse DNS at all, treating it as a sign of a potentially disposable or untrustworthy sending source.
- Does every VPS provider allow custom PTR records?
- Most do, but some budget providers restrict or don't support it at all — worth checking before building a mail server on an IP that can't get proper reverse DNS.
- What's forward-confirmed reverse DNS (FCrDNS)?
- It's when the PTR record's hostname, looked up forward again, resolves back to the original IP — a stricter check some mail servers use as an extra trust signal.