68bb4124_xchange_2010_and_Exchange_2007__EventID
[Description] The Microsoft Exchange Mail Submission service on a Mailbox server successfully notified a Hub Transport server that a message is awaiting submission (to the Hub). These are the events you’ll see on a Mailbox server. The SourceContext property provides the MDB Guid, Mailbox Guid, Event sequence number, Message class, Creation timestamp, and Client type. Client type can be User (Outlook MAPI), RPCHTTP (Outlook Anwhere), OWA, EWS, EAS, Assistants, Transport. [EventID] 
SUBMIT
Exchangepedia | Message Tracking from the command line in Exchange 2010 and Exchange 2007
EventID