resp Outbound Msg Id

1.3.6.1.4.1.334.3.1.2.3.1.13

The unique message identifier that the 'next hop' MTA assigned to the message. If the 'next' MTA uses a different messaging technology or identifier scheme, this identifier serves to correlate the message from MTA to MTA. If the 'next' MTA uses the same technology, this value is generally superfluous. If this is the last MTA in the delivery sequence, or if the next hop message id is unknown, this variable is null-valued.