Delayed Message: Messaging command in transmission too long
The email message has not yet been delivered becasuse mailing protocol parameters were not met as the commands used in message transmission were too long.
Try sending the message again in a while as this problem might be temporary or already in the process of being fixed.
If this error persists, contact the email provider for help.
4.5.6: Official Definition
A persistent transient failure is one in which the message as sent is valid, but persistence of some temporary condition has caused abandonment or delay of attempts to send the message. If this code accompanies a delivery failure report, sending in the future may be successful.
This enhanced status code SHOULD be returned when the server fails the AUTH command due to the client sending a [BASE64] response which is longer than the maximum buffer size available for the currently selected SASL mechanism. This is useful for both permanent and persistent transient errors.