Lookup for "550 2.0.0"
This status code indicates a successful delivery or other operation. Any details are simply notes.
Basic Status Code Details (550)
Requested action not taken: mailbox unavailable [E.g., mailbox not found, no access]
Enhanced Status Code Details (2.0.0)
Other undefined Status
Other undefined status is the only undefined error code. It should be used for all errors for which only the class of the error is known.