Many PC users are still using Microsoft Outlook as their main email application. It’s rather convenient because Outlook Express ships with the Windows operating system and the retail Outlook is part of Microsoft Office if I recall correctly. The biggest advantage of Outlook is in my opinion that it is already there, was never a fan of it though and recommend Thunderbird or any other email software - mostly.
Outlook Tools is a software that gives access to advanced Microsoft Outlook settings that would otherwise be hard to reach. You can use it for instance to unblock file extensions which would otherwise be only possible in the Windows Registry. Five tabs are accessible at the top of the software once it is started, they are General, Startup Switches, Clear MRU, New Mail Alert and Blocked Attachments.
Most of the options are self explanatory like the Clear MRU which simply clears several most recently used lists in Outlook such as the Search history. The software runs independently from Outlook and automatically detects the installed version. Supported are all versions of Outlook since Outlook 2000. There is no word about Outlook Express on the page and I was not able to test it, I would think that it is supported as well.