Gmail 503 5.7.0
No identity changes permitted
Gmail 503 5.7.0 means: no identity changes permitted. It is a permanent failure, so do not retry it unchanged. The client tried to change identity mid-session. Open a new connection to send as a different identity.
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
No identity changes permitted. For more information, go to About SMTP error messages.
| Who sends it | Gmail and Google Workspace |
|---|---|
| Basic code | 503: Bad sequence of commands (RFC) |
| Enhanced code | 5.7.0: Other or undefined security status |
| Permanent or temporary | Permanent (5xx) |
| Verifying the list prevents it | No |
What the sender should do
The client tried to change identity mid-session. Open a new connection to send as a different identity.
Would verifying the list have prevented Gmail 503 5.7.0?
No
This reply is about your sending setup, the message or the receiving system, not about whether the address exists, so verifying the list will not prevent it.
Common questions
- What does Gmail 503 5.7.0 mean?
- Gmail 503 5.7.0 means: no identity changes permitted. It is a permanent failure, so do not retry it unchanged. The client tried to change identity mid-session. Open a new connection to send as a different identity.
- Should I retry after Gmail 503 5.7.0?
- No. It is a permanent (5xx) failure, so the same message to the same address will fail again. Fix the cause first. The client tried to change identity mid-session. Open a new connection to send as a different identity.
- Would verifying my list have prevented Gmail 503 5.7.0?
- No. This reply is about your sending setup, the message or the receiving system, not about whether the address exists, so verifying the list will not prevent it.
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