I just found a nice little hidden/undocumented feature of Outlook (which works with at least version 2007). Do you know that you can modify the Subject Lines of Archived Outlook E-Mail?

Suppose, for example, you and some co-workers start exchanging e-mails about the company picnic. Somewhere along the way, the conversation shifts to sales forecasts, at which point someone pastes in some new figures. Now it's an e-mail you want to keep for future reference. Just one problem: The subject line still reads "company picnic." That won't be particularly helpful when you go looking for a message about sales figures. Fortunately, Outlook has a hidden feature that lets you edit an e-mail's subject line.

In Outlook, open the e-mail in question (you can't do this with message previews; you have to double-click the message to open it in a new window.) Click anywhere in the Subject line to place your cursor. Edit the subject as you see fit. Hit Enter, then accept whatever warning Outlook gives you. That's it! Now you can file the e-mail with a more fitting--and recognizable at-a-glance--subject line.

I found this trick from: http://www.computerworld.com/s/article/9135968/Be_More_Productive_in_Microsoft_Outlook?taxonomyId=12&pageNumber=1