A: When you create or enable a Microsoft Outlook rule, the rule applies only to future messages—not to content that has already been received. You have to run rules manually to retroactively apply them to existing content. When you create a new rule, you also have the option of applying the rule to existing messages by selecting a check box in the new rule creation confirmation dialog box, as Figure 1 shows.
Learn more: Outlook: Exporting Message Rules
If you want to manually apply a rule against messages already in your Outlook mailbox, you can select the Run Rules Now feature in the Rules and Alerts dialog box. In Outlook 2007 and earlier, you must separately select the rules that you want to manually run, as Figure 2 shows.
This method works fine, unless you have a long list of rules to apply. Outlook 2010 adds the Select All or Unselect All options in the Run Rules Now dialog box, as Figure 3 shows.
Probably the only times you might need to run all of your rules manually is if a lot of email is imported into your mailbox at once or perhaps if your rules have been disabled for a period of time. Outlook 2010 makes it easier to run all your rules manually by including the Select All and Unselect All options.