Gmail and Google Workspace · permanent error
555 5.5.2: syntax error in a command
Gmail could not parse a command or its parameters from your client, usually MAIL FROM or RCPT TO, and refused it.
- Gmail
- Provider
- Permanent (5xx)
- Class
- Sources checked
- Author
At a glance
- Code
- 555 5.5.2
- 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
555 5.5.2 Syntax error.
What it means
RFC 5321 defines reply 555 for MAIL FROM or RCPT TO parameters that are not recognized or not implemented, and Gmail pairs it with 5.5.2 for syntax errors in those commands. A second wording, 'Syntax error, goodbye', means Gmail is also closing the connection. Typical problems are an address written without angle brackets, a space after the colon, or an ESMTP parameter that Gmail did not offer in its EHLO reply. Google refers senders to RFC 5321.
Common causes
- MAIL FROM or RCPT TO written without angle brackets around the address.
- An ESMTP parameter on MAIL FROM or RCPT TO that Gmail did not advertise.
- Stray characters or spaces in the command.
How to fix it
- 01Check the exact command in the session log.
- 02Write addresses as MAIL FROM:<name@example.com>, with brackets and no space after the colon.
- 03Use only the ESMTP parameters that Gmail lists in its EHLO reply.
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
- 451 4.5.0SMTP protocol violation.Your server sent Gmail something that breaks the rules of the SMTP standard, RFC 5321, so Gmail stopped the transaction with a temporary error.
- 555Parameters not recognised.The server does not recognise, or does not implement, a parameter given with MAIL FROM or RCPT TO, so that command failed.
- 5.5.2SMTP syntax error.A command from the sending software could not be understood, because its syntax was wrong or the command was not recognised at all.
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