553 5.1.3: recipient address is not valid
Gmail rejected the recipient address because it is not written in a form the SMTP standard allows, so nothing can be sent to it.
- Gmail
- Provider
- Permanent (5xx)
- Class
- Sources checked
- Author
At a glance
- Code
- 553 5.1.3
- Provider
- Gmail and Google Workspace
- Temporary or permanent
- PermanentRefused for good: the message comes back to the sender, and resending it gets the same answer.
- Who has to act
- The sender. The fix is on the sending side: your domain, your server or your list.
- What the server says
553 5.1.3 The recipient address … is not a valid RFC 5321 address.
What it means
The recipient address breaks the address syntax of RFC 5321, the SMTP standard. The problem is the form of the address, before Gmail even looks for an account. Typical faults are spaces, unescaped special characters, a display name or angle brackets in the wrong place, two @ signs, or non-ASCII characters sent to a server that has not agreed to SMTPUTF8. Like most syntax errors it is permanent, so correct the address before sending again. Google refers senders to RFC 5321.
Common causes
- Spaces, commas or other characters that are not allowed in an address.
- A display name or brackets copied into the address field.
- Non-ASCII characters sent without SMTPUTF8 support.
- Software that builds the RCPT TO command incorrectly.
How to fix it
- 01Check the address exactly as your software sends it, from the logs if needed.
- 02Remove spaces, quotes and any display name, leaving only local-part@domain.
- 03If the address has non-ASCII characters, make sure your software supports SMTPUTF8, or ask the recipient for an ASCII address.
- 04Resend once the address is corrected.
Sources
What this page rests on, checked on 20 Oct 2026. The explanation is ours; the reply text is the server's.
- Gmail SMTP errors and codes (Google Workspace Admin Help)knowledge.workspace.google.com
Related codes
- 553 5.1.7Sender address is not valid.Gmail rejected the address in your MAIL FROM command because it does not follow the SMTP address syntax, so it will not take mail from it.
- 553Mailbox name not allowed.The server refused the address because the mailbox name is not allowed there, most often because it is written incorrectly.
- 5.1.3Recipient address is malformed.The recipient address breaks the rules for how an email address must be written, so the server refused it before checking whether it exists.
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