The Search facility is very good in Outlook (and in OWA) and can be used across all folders. In Outlook searches can be refined on a range of criteria; seaching is possible within all types of folders (mail, contacts, calendars). This is described in the document  Making Best Use of Microsoft Outlook 2010 using Exchange  (pages 37-39 of 86-page PDF).

Other search facilities are available within Outlook: Search folders allow you to create virtual folders of messages based on particular criterion. Some examples are listed below:

• Messages From Specific People
• Important Mail - all the messages sent to you marked as important.
• Mail with Specific Words to keep track of correspondence relating to a particular topic

How to set up search folders is described in the document Search Folders - extra search functions in Outlook [5-page PDF].

Note: You will require Adobe Acrobat Reader on your computer to download pdf files. This software can be downloaded from the Adobe website.