Permanent failure — do not retry
SMTP 550 5.7.25
no PTR record for sending IP (Gmail)
SMTP 550 5.7.25 means Gmail rejected the message because the sending IP has no PTR (reverse DNS) record, or the PTR does not match a forward DNS record. Google requires reverse DNS on every sending IP. The fix is on your sending server, not the recipient's.
How it appears
550 5.7.25 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.
What causes it
- 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.
How to fix it
In order — try the first one first.
- Ask whoever controls the IP (your host or ISP) to set a PTR record for it.
- Make sure the PTR hostname has an A record pointing back at the same IP.
- Use that hostname in your server's HELO or EHLO greeting.
- Do not suppress recipients. The rejection is about your IP.
Common questions
- What does SMTP 550 5.7.25 mean?
- SMTP 550 5.7.25 means Gmail rejected the message because the sending IP has no PTR (reverse DNS) record, or the PTR does not match a forward DNS record. Google requires reverse DNS on every sending IP. The fix is on your sending server, not the recipient's.
- Should I retry a 550 5.7.25 error?
- No. 550 is a permanent failure, so the message will never be delivered no matter how many times you try. Remove the address — repeated sends to permanent failures are one of the main signals mailbox providers use to throttle a sender.
- How do I fix SMTP 550 5.7.25?
- Ask whoever controls the IP (your host or ISP) to set a PTR record for it.
Other 550 replies
- 550 5.1.1 — mailbox does not exist
- 550 5.7.1 — message refused by policy
- 550 5.4.1 — recipient address rejected, access denied
- 550 5.2.1 — mailbox disabled, not accepting messages
- 550 — mailbox unavailable
- 550 5.1.0 — address rejected, other address status
- 550 5.1.10 — recipient not found (Microsoft 365)
- 550 5.1.8 — bad outbound sender (Microsoft 365)
- 550 5.4.5 — daily sending limit exceeded (Gmail)
- 550 4.4.7 — message expired in the queue
- 550 5.7.26 — blocked, sender unauthenticated (Gmail)
- 550 5.7.27 — SPF authentication failed (Gmail)
- 550 5.7.28 — unusual rate of unsolicited mail (Gmail)
- 550 5.7.23 — SPF violation (Microsoft 365)
- 550 5.7.124 — sender not in allowed senders list (Microsoft 365)
- 550 5.7.509 — DMARC failed, policy reject (Microsoft 365)
- 550 5.7.606-649 — banned sending IP (Microsoft)
- 550 5.7.705 — tenant has exceeded threshold (Microsoft 365)
- 550 5.7.708 — traffic not accepted from this IP (Microsoft 365)
- 550 5.7.750 — blocked from sending from unregistered domains (Microsoft 365)
- 550 5.7.515 — authentication required for high-volume senders (Outlook.com)
- 550 5.7.1 S3140 — IP range on Outlook.com block list
Last reviewed 2026-09-11