Lookup for "214 4.6.1"
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 (4.6.1)
Media not supported
The media of the message is not supported by either the delivery protocol or the next system in the forwarding path. This is useful only as a permanent error.