Had to confirm or deny that an email from a non-exchanged sourced email was delivered to the recipient.  I found the following post, that got my down the right track: http://www.itsupportguides.com/exchange-2010/exchange-2010-message-tracking-log-with-time-date/

The sample below only searches the logs for one particular sender.

1. Connect to your Exchange 2010 server via your preferred method.
2. Open the Exchange Powershell Console.
3. Run the following command (more options available via help):

Get-MessageTrackingLog -Sender "someone@domain.com" | Select timestamp, recipients, messagesubj
ect, EventID

Posted from Flint, Michigan, United States.