OWA 2016

  1. Navigate to Options > Automatic replies ( or Options > Options > Automatic replies):

  1. Automatic replies can be sent either to users inside of your organization or to everyone. The wording can be different. You can also specify the time range in which the auto-replies will be sent (if you don’t specify a start and end time, auto-replies will be sent until you select the Don't send automatic replies option):