550 5.5.0: requested action not taken: mailbox unavailable
A general permanent refusal: the mailbox is not available for delivery.
Permanent failure (hard bounce)
What 550 5.5.0 means
A catch-all text from many servers. It usually means the mailbox does not exist, but without the specific enhanced code (5.1.1, 5.2.1) you cannot tell whether it is missing, disabled or blocked.
Common causes
- A non-existent mailbox
- A disabled or suspended account
- A server that uses generic wording for all permanent refusals
How to fix it
- Read the human-readable text after the code for clues
- Verify the address independently before retrying
What to do with the address
Treat repeated 5.5.0 results as invalid and remove the address.
Check an address now with the free email checker, or look at a domain's mail setup with the email domain checker, MX lookup and SPF checker.
Related error codes
Frequently asked questions
- What does 550 5.5.0 mean?
- A general permanent refusal: the mailbox is not available for delivery. A catch-all text from many servers. It usually means the mailbox does not exist, but without the specific enhanced code (5.1.1, 5.2.1) you cannot tell whether it is missing, disabled or blocked.
- Is 550 5.5.0 a hard bounce or a soft bounce?
- Permanent failure (hard bounce). The address will keep failing, so remove it.
- What should I do with the address after 550 5.5.0?
- Treat repeated 5.5.0 results as invalid and remove the address.