Server-based rules If you are using a Microsoft Exchange Server account , some rules that you create are server-based rules. These rules run on your mailbox on the Exchange mail server, even when Outlook isn’t running on your computer. Server-based rules must apply to messages when they are first delivered to your Inbox , and the rules must be able to run until they are completed on the server. For example, a rule that specifies that a message be printed can’t run until it is completed on the server. If a rule can’t be applied on the server, it is applied when you start Outlook and becomes a client-only rule.