A: I sometimes create new Outlook rules on the fly while reviewing email messages. Outlook makes this process simple with a button in the Ribbon of an open message. In Outlook 2007, you select Create Rule in the Actions tab of an open message, and in Outlook 2010, Create Rule is found in the drop down menu of the Rules button. Outlook offers simple rule creation with common message properties through this method. You can select Advanced at the bottom of the Create Rule dialog box to show all of the options for new rule creation in the Rules Wizard. The most common rule I see is the simple act of moving a message to a subfolder based on sender or subject.
When you create such a rule in Outlook, you're presented with the option of applying the rule to messages already received, as Figure 1 shows.
Figure 1: Outlook dialog box with the option to run a new rule on messages already in the current folder
Outlook searches your Inbox (or whatever folder you launched this message from), checking for items that match the parameters you set in the rule. If you have a lot of messages in the folder, typically your Inbox, this action can take some time. Of course, this functionality is powerful, requiring no effort from the user, except that of patience. However, you won't be able to access anything else in Outlook while it searches mail folders for items that apply to your newly created rule!
If you have a significant number of messages stored in your Inbox, Outlook can take minutes to apply the rule against every message therein. If the folder you're searcing is a local .pst file, it might take even longer. I found that with 1,000 messages in a .pst folder, it was faster to manually sort the messages by Subject (or Sender, or whichever parameter you used in the rule), then drag-and-drop the content to the intended subfolder.
When I tested a rule on a .pst folder with 25,000 messages, Outlook took four minutes to finish. Sometimes, it's just easier to do things yourself, especially if you're as impatient as I am.