Gmail 553 5.1.2
Recipient domain not found
Gmail 553 5.1.2 means: recipient domain not found. It is a permanent failure, so do not retry it unchanged. Gmail could not find the recipient domain. Check for a typo or trailing punctuation; otherwise remove the address.
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
We weren't able to find the recipient domain. Please check for any spelling errors and make sure you didn't enter any spaces, periods, or other punctuation after the recipient's email address. For more information, go to Fix bounced or rejected emails.
| Who sends it | Gmail and Google Workspace |
|---|---|
| Basic code | 553: Requested action not taken: mailbox name not allowed (e.g., mailbox syntax incorrect) (RFC) |
| Enhanced code | 5.1.2: Bad destination system address |
| Permanent or temporary | Permanent (5xx) |
| Verifying the list prevents it | Yes, verification catches this |
In practice
Gmail checks that the recipient domain exists before accepting the address. Google's text points at common causes: a misspelled domain, or a space, period or other punctuation typed after the address. Exported lists sometimes carry trailing dots or semicolons, which produce this error for addresses that are otherwise fine. Clean the formatting first, then remove addresses whose domains really do not exist.
What the sender should do
Gmail could not find the recipient domain. Check for a typo or trailing punctuation; otherwise remove the address.
Would verifying the list have prevented Gmail 553 5.1.2?
Yes, verification catches this
A mailbox check asks the recipient's server whether the address and domain can receive mail, without sending anything, so the address is flagged before the send instead of bouncing against your domain.
Common questions
- What does Gmail 553 5.1.2 mean?
- Gmail 553 5.1.2 means: recipient domain not found. It is a permanent failure, so do not retry it unchanged. Gmail could not find the recipient domain. Check for a typo or trailing punctuation; otherwise remove the address.
- Should I retry after Gmail 553 5.1.2?
- No. It is a permanent (5xx) failure, so the same message to the same address will fail again. Fix the cause first. Gmail could not find the recipient domain. Check for a typo or trailing punctuation; otherwise remove the address.
- Would verifying my list have prevented Gmail 553 5.1.2?
- Yes, verification catches this. A mailbox check asks the recipient's server whether the address and domain can receive mail, without sending anything, so the address is flagged before the send instead of bouncing against your domain.
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