smtp;501 5.1.3 Invalid address [outlook.com]
The receiver refused the message for good and points at an addressing problem (the recipient or sender address itself) (enhanced status 5.1.3). Use the wording above to pin down the exact fix.
Email provider · 5.x.x permanent failure
Outlook SMTP 501 Errors: Every Bounce Response Explained
Every SMTP 501 response on record from Outlook (hotmail.com, outlook.com, msn.com, live.com), with the verbatim text, the enhanced status code, a severity rating and a plain-English fix.
A syntax error in the command arguments, almost always a malformed or invalid address in the envelope or headers. It stays permanent until the address is corrected.
- Provider
- Outlook
- Code
- 501 (5xx)
- Responses
- 1
- Highest severity
- Low
Outlook SMTP 501 responses
Outlook SMTP 501 questions
›What does an SMTP 501 error from Outlook mean?
A syntax error in the command arguments, almost always a malformed or invalid address in the envelope or headers. It stays permanent until the address is corrected. At Outlook, it is a permanent rejection, and the specific reason is in the enhanced status code and message text of each response below.
›How do I stop Outlook from returning SMTP 501?
Match your bounce text to one of the responses below and follow its guidance. Recipient-side wording means fix the address. Authentication or reputation wording (SPF, DKIM, DMARC, blocklist) means fix your sending setup, and check Outlook's postmaster documentation.