550 5.7.30 is a permanent SMTP reply meaning gmail blocked the message: dkim did not pass. The message had no valid DKIM signature. Either it was not signed, the public key was not found in DNS, or the signature did not match the message.
What 550 5.7.30 means
The message had no valid DKIM signature. Either it was not signed, the public key was not found in DNS, or the signature did not match the message.
Common causes
DKIM is not turned on for the sending service
Most commonGoogle Workspace, Microsoft 365 and most ESPs need you to publish a key and switch signing on. Until then mail goes out unsigned.
The DKIM record is wrong or missing in DNS
CommonA typo, a split TXT string, or a record under the wrong selector means the receiver cannot find the key.
Something changed the message after signing
Less commonA footer, link rewriter or security gateway that edits the body breaks the signature.
How to fix 550 5.7.30
- 1
Find the selector in use
The DKIM-Signature header in a sent message shows s= (selector) and d= (domain). If there is no header, signing is off.
- 2
Publish the key and turn on signing
Copy the exact DKIM record from your provider, publish it at selector._domainkey.yourdomain, and enable signing in the provider console.
- 3
Check the key
Use the free DKIM checker with your selector to confirm the key is published and is at least 1024 bits (2048 is better).
Confirm your domain is set up correctly
Most delivery failures — permanent or temporary — trace back to authentication or reputation. Run a free EmailHealth check to confirm SPF, DKIM, DMARC, blacklist status, and TLS are all healthy for your sending domain. If you send in volume, free daily monitoring will alert you before a small issue becomes a flood of bounces.