Gmail 550 5.7.25 "No PTR Record": Fix Reverse DNS on Your Sending IP

Gmail's 550 5.7.25 means the IP that sent the message has no PTR record, or the PTR does not match a forward DNS record. Google's text reads "This message was blocked because the sending IP address doesn't have a PTR record, or the forward DNS entry of the PTR record doesn't match the sending IP address." The problem is on your sending server, not the recipient's.

The 550 5.7.25 code page has the summary.

Reading the code

Part	Value	Meaning
Reply code	550	Requested action not taken
Class	5	Permanent failure
Subject	7	Security or policy status
Detail	25	Reverse DNS validation failed

RFC 3463 defines the class and subject, and RFC 7372 added the detail 5.7.25 for a failed reverse DNS validation. Google's text is in its Gmail SMTP error reference.

What a PTR record is

A PTR record maps an IP address back to a hostname. Reverse DNS is the lookup from IP to name, and forward DNS is the lookup from name to IP. Google wants the two to agree: the IP's PTR points to a hostname, and that hostname has an A record that points back at the same IP. Our guide to reverse DNS and PTR records for email goes through it.

Why it happens

• The sending IP has no reverse DNS record at all.
• The PTR hostname does not resolve back to the same IP.
• Mail is going out from a new server or cloud IP that was never set up for sending.

Fix it

1. Find the sending IP in the bounce or the message headers. The email header analyzer lists the hops.
2. Look up its PTR with the reverse DNS lookup.
3. Ask the IP's owner to set the PTR. That is your host or ISP, not your DNS provider.
4. Make sure the hostname has an A record pointing at the same IP.
5. Use that hostname in your server's HELO or EHLO greeting. See the HELO command rejected fix.

If you send through an email service, the service owns the IP and should already have this set. Contact them rather than trying to change anything yourself.

Checking before you send

For a server you run, find IPs with no reverse DNS before sending shows how to test every sending IP in one pass, and the bulk reverse DNS lookup does it for a list.

Keep the address side clean

This code does not come from your list, but every bounce still counts against your sending reputation, so the addresses you do send to should be real. Upload your list on the verify page: the first 100 email checks are free with a Google sign-in, no card. Each address comes back valid, risky or invalid with a reason such as "Mailbox not found" or "Accepts all addresses", and nothing is sent to anyone on the list. For larger or recurring lists, see bulk email verification, list cleaning and pricing.