Lookup for "214 2.1.7"
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 (2.1.7)
Bad sender's mailbox address syntax
The sender's address was syntactically invalid. This can apply to any field in the address.