Lookup for "250 4.4.2"
Temporary Error - This status code indicates a transient issue and may resolve itself.
Basic Status Code Details (250)
Requested mail action okay, completed
Enhanced Status Code Details (4.4.2)
Bad connection
The outbound connection was established, but was unable to complete the message transaction, either because of time-out, or inadequate connection quality. This is useful only as a persistent transient error.