SYMPTOM:
When trying to open an Excel report generated from Strategy Developer 10.x using the File menu "Email Report As" option, the following error occurs:
This file is not in a recognizable format.

This issue occurs when opening an Excel attachment that was created from a Strategy Developer machine with Excel 2007 on it and trying to open the file from Excel 2003.
CAUSE:
This is a known issue and has been logged with the Strategy Technology department.
ACTION:
Strategy will continue to investigate and post updates as soon as they are available.
WORKAROUND:
Users should open the file through Microsoft Excel 2007 or utilize the Microsoft provided viewer:
http://www.microsoft.com/downloads/details.aspx?familyid=1CD6ACF9-CE06-4E1C-8DCF-F33F669DBC3A&displaylang=en