What DNS issues commonly cause “no reverse DNS” rejections?
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Your email just got rejected with a "no reverse DNS" error. Before you panic, this is actually one of the more fixable delivery problems out there. But you do need to understand what's actually being checked.
When a receiving mail server gets your message, it looks up your sending IP address in reverse. It's asking: "Does this IP have a name, and does that name point back to the same IP?" That lookup is called a reverse DNS check, and it uses a special DNS record type called a PTR record. Think of it as the mail server asking for your return address before it lets you in.
There are three common reasons this check fails.
No PTR record at all. Your sending IP has no name assigned to it. The mail server looks it up and finds nothing. Many receiving servers will reject the connection outright at this point. This is the most common cause and also the easiest to fix. You (or your hosting provider) need to create a PTR record for your sending IP that points to a meaningful hostname, like mail.yourdomain.com.
The PTR record exists but doesn't resolve forward. This is trickier. Your IP has a hostname in DNS, but when the mail server then checks whether that hostname points back to your IP, it gets nothing. This is called a Forward-Confirmed Reverse DNS check (FCrDNS), and it's a two-step verification. Step one: IP to hostname. Step two: hostname back to IP. Both have to work. If your PTR record says mail.yourdomain.com but there's no matching A record in your forward DNS, you fail step two and the receiving server treats it as invalid.
A generic or dynamic-looking PTR record. Some servers will accept you technically but still penalize you. If your PTR resolves to something like 192-0-2-1.pool.dynamic.isp.com, it signals that you're sending from a residential or dynamically-assigned IP rather than a dedicated mail server. Spam filters see that pattern constantly from compromised home machines. Even if your PTR technically resolves forward and back, a generic hostname like that raises flags.
The fix for all three cases follows the same path. Ask your hosting provider or ISP to set a PTR record for your sending IP. The hostname it points to should be something meaningful (not auto-generated), like mail.yourdomain.com. Then make sure your forward DNS has an A record for that same hostname pointing back to your sending IP. Once both are in place, you've got a clean FCrDNS setup.
And if you're on a shared sending platform, this is usually handled for you. If you're on a dedicated IP, it's on you (or your team) to configure it. Either way, it's worth double-checking. A broken PTR can stop your emails before they're even considered for delivery, no matter how good your content or email authentication looks.
Not sure if your PTR is set up correctly? Our SOS hotline is free and we can walk you through exactly what to check and what to tell your hosting team.
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