Summary:
Offline Timesheet sent from the Web TimeSheet application consists of a HTML file. When one downloads / opens this HTML file directly from Outlook Web Access (OWA) interface, a blank page is displayed. One can also see that the saved HTML file is hardly a KB than the original file size which is much bigger size as seen in the email attachment.

Microsoft has a feature called Safe HTML filtering built in to Outlook Web Access for Exchange Server 2003. The purpose of this feature is to block HTML files in the email which may contain any scripts or any potentially unsafe content in the email. If one access the email using Outlook 2003 on the other hand, they would not see such a problem. OWA was built by Microsoft with high security requirements for safer email environment.

This logic is built in to OWA by Microsoft and unfortunately cannot be turned off. Further details about this feature is available from Microsoft in the link
https://support.microsoft.com/kb/899394/

We do not have any control over the OWA feature by Microsoft's Exchange server and therefore suggest to have users access Offline Timesheet HTML attachment via Outlook 2003 interface or public email address, if possible.

Note:
This applies to Microsoft Exchange server 2003 environment.