A common goal is to filter incoming messages, perhaps sending an automatic response, forwarding the messages to another account, or automatically rejecting or discarding some based upon material in the messages' headers or bodies. One way to do this is via the DELIVER facility discussed in Chapter 5.

If your messages are delivered to the native message store (VMS MAIL mailbox) or to a PMDF popstore or PMDF MessageStore account, your system administrators may have chosen to enable another option: PMDF message filtering. If your system administrators have chosen to enable it, PMDF provides a web-based interface through which you can specify a vacation notice, specify a forwarding address, and construct and manage your own message screening rules. These are collectively known as mailbox filters.