smtp;550 5.1.1 <[email protected]>: Recipient address rejected: User unknown
The address does not exist, or is no longer active, at this provider. Remove it from your list and check for a typo in the local part or the domain.
Email provider · 5.x.x permanent failure
Hey SMTP 550 Errors: Every Bounce Response Explained
Every SMTP 550 response on record from Hey, with the verbatim text, the enhanced status code, a severity rating and a plain-English fix.
The mailbox is unavailable and the message is rejected for good. This is the catch-all permanent failure, covering everything from an unknown address to an authentication failure to a reputation block, so the wording after the number is what actually tells you the reason.
- Provider
- Hey
- Code
- 550 (5xx)
- Responses
- 1
- Highest severity
- Low
Hey SMTP 550 responses
Postmaster & documentation
Hey SMTP 550 questions
›What does an SMTP 550 error from Hey mean?
The mailbox is unavailable and the message is rejected for good. This is the catch-all permanent failure, covering everything from an unknown address to an authentication failure to a reputation block, so the wording after the number is what actually tells you the reason. At Hey, 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 Hey from returning SMTP 550?
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 Hey's postmaster documentation.