Text view is based on the case setting time zone.  Native sent date/time is calculated based on the IGC engine which uses the server time zone. 

Example:  If a Message is sent at 9 am EST which was processed on a server set to PST time zone and the Case was setup with GMT time, the following results would be observed:

Text View would show 2 pm
Native View would show 6 am

*Note* when viewing the original source, the email will reflect the client's time zone as well.  Therefore a PC set to EST will see the original email at 9 am.  If the a client PC is set to PDT, then that PC will see the original email at 6 am.
 

The case settings should be set to the same time zone as the Clearwell server.