Mail errors · Gmail

What does “550 5.7.25 This message was blocked because the sending IP address doesn't have a PTR record” mean?

The server that sent the message has no reverse DNS name, or its name does not point back to it.

Last read from the sources at the foot of this page.

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Gmail bounce
Mail Delivery Subsystem
550 5.7.25

This message was blocked because the sending IP address doesn't have a PTR record

As Gmail prints it.
01

What does it mean?

A PTR record turns an IP address back into a host name. Gmail requires the sending address to have one, and the name to point back to the same address.

02

What exactly does the source say?

550 5.7.25 This message was blocked because the sending IP address doesn't have a PTR record, or the forwarding DNS entry doesn't reference the sending IP address. Gmail requires that sending IP addresses have a PTR record. Learn more about requirements for sending IP addresses. To learn more about Gmail requirements for bulk email senders, visit Email sender guidelines.

Gmail's page writes domain-name and ip-address where your bounce shows your own domain and the sending address.

Same fix: 451 4.7.23
451 4.7.23 ip-address The sending IP address for this message doesn't have a PTR record, or the PTR record's forward DNS entry doesn't match the sending IP address. To protect users from spam, your email has been temporarily rate limited. To learn more about IP address requirements for sending to Gmail, visit the IP addresses section of our sender guidelines. To learn more about Gmail requirements for bulk email senders, visit Email sender guidelines.
Same fix: 421 4.7.0
421 4.7.0 The IP address sending this message does not have a PTR record, or the corresponding forward DNS entry does not point to the sending IP. To protect our users from spam, email sent from your IP address has been temporarily rate limited. For more information, go to Email sender guidelines.
03

Why would a small firm see it?

Mail sent straight from a web server, an office server or a device, instead of through your mail provider. Large mail providers set these records for their own servers.

04

How do I fix it?

  1. Find which server sent the message: the bounce gives its IP address.
  2. Where you can, send that mail through your mail provider instead, with a username and password.
  3. Where the server must send directly, a PTR record is set by whoever holds the IP address: the hosting company or the internet provider.It is not set among your domain's own records.
05

What else do the sources say?

Ensure that sending domains or IPs have valid forward and reverse DNS records, also referred to as PTR records.

Sources

Where does this come from?

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