In order to set up autoreply for distribution list, follow these steps:

  1. create a user mailbox with the intended email address of the distribution list, e.g.
  2. create a distribution list of another name, e.g.
  3. set Out Of Office reply on the user's mailbox
  4. set forwarding on the user mailbox to the distribution list with Save a copy option checked
  5. grant Send As permissions to user's mailbox for the ditribution list

Note: Out of Office reply is sent to each sender only once. In order for each sender to receive an Out of Office reply again, Ouf of Office Assistant must be turned off and back on.

Alternatively, instead of using the Out of Office assistant, you can use a server-side rule to set up an auto-reply. Using server-side rules allows you to get round the one reply to one sender limitation. You do not need to have Outlook or OWA open for the rule to work. Read the Knowledge Base article How Do I Set Up Out Of Office Assistant? for more information.