Interestingly, I note that the trusted old Lookout email search tool is mentioned quite a bit on the Lookeen pages.

Lookout was amazing !!! Found documents buried in layers of email wrappers, zip files, etc and was able to be coaxed into searching document shares, etc.

Microsoft purchased Lookout, and subsequently support was dropped from Vista / Office 2007 onwards -

https://lookeen.com/blog/lookout-an-obituary

I think I managed to kludge it once for a more recent version of Office (Outlook 2010?),