68bb4124_xchange_2010_and_Exchange_2007__EventID
[Description] Message received. The Source field is STOREDRIVER for messages submitted by Store Driver (from a Mailbox server), or SMTP for messages a) received from another Hub/Edge b) received from an external (non-Exchange) host using SMTP c) submitted by SMTP clients such as POP/IMAP users. [EventID] 
RECEIVE
Exchangepedia | Message Tracking from the command line in Exchange 2010 and Exchange 2007
EventID