Gmail 550 5.7.28
Blocked: unusual rate of unsolicited mail
Gmail 550 5.7.28 means: blocked: unusual rate of unsolicited mail. It is a permanent failure, so do not retry it unchanged. Gmail blocked mail from your IP for an unusual rate of unsolicited email. Stop the campaign, remove unengaged and unverified addresses, and resume slowly.
Gmail’s exact wording
Quoted from Google Workspace Admin Help: Gmail SMTP errors and codes, checked 2026-11-05. Placeholders are Gmail’s own.
Reply text
There is an unusual rate of unsolicited email originating from your IP address. To protect our users from spam, email sent from your IP address has been blocked. To review our bulk email senders guidelines, go to Email sender guidelines.
| Who sends it | Gmail and Google Workspace |
|---|---|
| Basic code | 550: Requested action not taken: mailbox unavailable (e.g., mailbox not found, no access, or command rejected for policy reasons) (RFC) |
| Enhanced code | 5.7.28: Mail flood detected |
| Permanent or temporary | Permanent (5xx) |
| Verifying the list prevents it | Partly |
In practice
This is the permanent form of the unsolicited-rate limit: Gmail has blocked mail from your IP rather than just slowing it. It usually follows a period of 421 4.7.28 deferrals that the sender ignored, or a sudden large send from a new IP. Stop the campaign, find the list segment that caused the spike, and resume at a lower volume to engaged recipients only.
What the sender should do
Gmail blocked mail from your IP for an unusual rate of unsolicited email. Stop the campaign, remove unengaged and unverified addresses, and resume slowly.
Would verifying the list have prevented Gmail 550 5.7.28?
Partly
The reply is not only about one address, but providers weigh how often a sender hits addresses that do not exist. Removing bad addresses before sending lowers that signal.
Common questions
- What does Gmail 550 5.7.28 mean?
- Gmail 550 5.7.28 means: blocked: unusual rate of unsolicited mail. It is a permanent failure, so do not retry it unchanged. Gmail blocked mail from your IP for an unusual rate of unsolicited email. Stop the campaign, remove unengaged and unverified addresses, and resume slowly.
- Should I retry after Gmail 550 5.7.28?
- No. It is a permanent (5xx) failure, so the same message to the same address will fail again. Fix the cause first. Gmail blocked mail from your IP for an unusual rate of unsolicited email. Stop the campaign, remove unengaged and unverified addresses, and resume slowly.
- Would verifying my list have prevented Gmail 550 5.7.28?
- Partly. The reply is not only about one address, but providers weigh how often a sender hits addresses that do not exist. Removing bad addresses before sending lowers that signal.
The same code elsewhere
Sources
- Google Workspace Admin Help: Gmail SMTP errors and codes (checked 2026-11-05)
- IANA: SMTP Enhanced Status Codes registry (checked 2026-11-05)
- RFC 5321: Simple Mail Transfer Protocol, section 4.2.3 (reply codes) (checked 2026-11-05)
Registry and provider wording is quoted exactly; guidance is written by the SimpleVerifier Team.
SimpleVerifier Team · Last checked against the sources 2026-11-05