How to create a custom rule for Outlook automatic replies If you simply can't miss a message from your boss - even when you're in tropical paradise and really shouldn't be working - and you prearranged to use an email subject line "code word" (such as "IMPORTANT") so the boss can reach you if absolutely necessary, you can create custom Outlook out-of-office message rules to make sure crucial messages get sent to you via a personal mail account, for example.