550 Requested action not taken: mailbox unavailable

Meaning

The mailbox is unavailable or policy rejected.

Common causes

• User unknown.
• Policy block.

How to fix

1. Remove address.
2. Check policy.

Example bounce

550 Requested action not taken: mailbox unavailable

Related codes

• 550 5.1.1 User unknown / invalid address
• 550 5.1.2 Bad destination system address
• 550 5.1.10 Recipient not found