Why can’t I add the PTR in my DNS?

Reverse DNS is controlled by whoever holds the IP block, your ISP or hosting provider, so the change is requested from them.

Does Gmail require PTR for IPv6?

Yes. Google requires valid forward and reverse DNS for sending IPs, and IPv6 senders without it are commonly rejected with 5.7.25.

5.7.25 bounce: reverse DNS validation failed

5.7.25Reverse DNS validation failedPermanent: retrying will not help

Typical wording

550 5.7.25 Reverse DNS validation failed

What it means

RFC 7372 defines X.7.25, “reverse DNS validation failed”. The receiver looked up the PTR record for your connecting IP and either found none, or found a name that does not resolve back to the same IP (forward-confirmed reverse DNS, FCrDNS).

Gmail uses 550 5.7.25 for exactly this when IPv6 or IPv4 senders lack a matching PTR, and many other receivers treat missing reverse DNS as a strong spam signal. The check is about the IP, not the domain in your From address, so SPF, DKIM, and DMARC cannot compensate.

A temporary 4.7.25 can appear when the PTR lookup timed out at the receiver. The 5.7.25 form means the lookup worked and the answer was wrong or empty.

Likely causes

No PTR record at all for the sending IP, common on new VPS and cloud servers.
A PTR pointing at a generic provider name (for example 203-0-113-10.provider.example) that does not resolve back.
A PTR name whose A or AAAA record points somewhere else after a migration.
IPv6 sending enabled on a server that only has reverse DNS set for IPv4.

How to fix it

Find your sending IP (from the bounce or your MTA log) and look up its PTR record.
Ask whoever owns the IP, your hosting or cloud provider, to set the PTR to your mail host name, for example `mail.example.com`; you cannot set it in your own domain’s zone.
Create a matching A (and AAAA) record so `mail.example.com` resolves back to the same IP.
Use the same name in your server’s EHLO greeting, and if IPv6 lacks a PTR, set one or disable IPv6 sending.

Checks that apply

Your domain or sending IP (fills in the checks below)

Reverse DNS (PTR) Looks up the reverse DNS for your sending IP and checks that the name resolves back, which is the exact 5.7.25 test.
A Record Confirms the forward A record of your mail host name points at the sending IP.
SMTP Diagnostics Shows the EHLO name your server announces, which should match the PTR name.

FAQ

Why can’t I add the PTR in my DNS?: Reverse DNS is controlled by whoever holds the IP block, your ISP or hosting provider, so the change is requested from them.
Does Gmail require PTR for IPv6?: Yes. Google requires valid forward and reverse DNS for sending IPs, and IPv6 senders without it are commonly rejected with 5.7.25.

All 191 bounce codes