Lookup for "214 4.2.0"
Temporary Error - This status code indicates a transient issue and may resolve itself.
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 (4.2.0)
Other or undefined mailbox status
The mailbox exists, but something about the destination mailbox has caused the sending of this DSN.