Lookup for "214 2.1.3"
This status code indicates a successful delivery or other operation. Any details are simply notes.
Basic Status Code Details (214)
Help message [Information on how to use the receiver or the meaning of a particular non-standard command; this reply is useful only to the human user]
Enhanced Status Code Details (2.1.3)
Bad destination mailbox address syntax
The destination address was syntactically invalid. This can apply to any field in the address. This code is only useful for permanent failures.