553 5.1.7: sender 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.
- Gmail
- Provider
- Permanent (5xx)
- Class
- Sources checked
- Author
At a glance
- Code
- 553 5.1.7
- 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 5.1.7 The sender address … is not a valid RFC 5321 address.
What it means
This is about the envelope sender, the address your server gives in MAIL FROM, where bounces are returned. Gmail found it malformed under RFC 5321. Mail servers rarely get this wrong, so it usually comes from an application, script or device that builds its own SMTP commands: a missing domain, a display name inside the brackets, spaces, or a bare user name with no @. The fix is in the configuration of the sending software, and an unchanged retry fails again.
Common causes
- An application or device configured with a sender address that has no domain.
- A display name or quotes included in the MAIL FROM address.
- Spaces or invalid characters in the configured sender address.
How to fix it
- 01Find the MAIL FROM address in your sending logs.
- 02Set the sender to a complete address, such as name@yourdomain.com, in the application or device.
- 03Keep display names in the From header only, never in MAIL FROM.
- 04Send a test message once the setting is changed.
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 5.1.3Recipient 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.
- 553Mailbox name not allowed.The server refused the address because the mailbox name is not allowed there, most often because it is written incorrectly.
- 5.1.7Sender address is malformed.The sender address in the envelope (MAIL FROM) is written in a way the receiving server cannot accept, so it refused the message.
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