Rules can be used to filter messages into other folders, to flag them for special attention, or to send the message to another address.

1. Right-click on a message you want to create a mailbox rule for and select Advanced Actions, and then Create rule... (When using a mouse without a right-click, control-click the message).
2. Enter a descriptive name for the rule in the Name box.
3. Rules will have conditions to be met and actions to be taken once all the conditions are met. A default set of conditions will be created, based on the qualities of the message chosen.
4. Under When the message arrives, and it meets all of these conditions, use the pull-down menu to select the appropriate type of condition. Some conditions have further options to them.
5. To add another condition, click the Add condition button and adjust the new condition with the pull-down menu.
6. Click the X to the left of a condition to remove it.
7. Under Do all of the following, use the pull-down menu to select the appropriate type of action.
8. An exception can be added to a rule. For example, you may want to mark messages from a particular person, but not mark those messages which do not contain attachments. To use this, in the Except if it matches any of these conditions section, click the Add condition button and adjust the new condition with the pull-down menu, as above.
9. Scroll to the top of the window and click the OK button to save your rule.
10. All rules will normally be applied to all messages, each in its turn. You can choose to have a particular message ignore your subsequent rules if it meets the conditions for a particular rule. This option is turned on by default. Uncheck the Stop processing more rules checkbox if you want this particular rule to be one of a set applied to a particular type of message.
11. To manage existing rules, click on the gear icon in the upper right corner and select View all Outlook settings.
12. Under the Mail menu, you can view your inbox rules by selecting the Rules section.
13. You can use the + Add new rule button to add a new rule, the Pencil button to edit an existing rule, the Trash can button to delete an existing rule, or the Up and Down arrow buttons to move the order of a rule in the set of rules.

More information can be found on Microsoft's Support page for managing rules on the Outlook Web App or on the Outlook desktop app.