I think Sonasoft is a red herring. It's an Obama loving company that will give whatever answers the IRS needs. The IRS could have gotten the email off the backup tapes. The committee needs to get the IT IRS techs in and then representatives of the storage companies that the IRS uses.
Gowdy is artful in getting the rat to the trap:
Crumb. Crumb. Crumb. Crumb. ZAP!
Jordan was another who effectively chewed on the commish.