How do I set up and auto response to messages I recieve when I'm gone for a week?

Auto response

As far as I know this can only be done with GMail and Exchange servers.

If you used Automatic Setup for your GMail account there is nothing to configure. If you set your account up as POP3, you will not be able to use Automatic Replies as the Google Service protocol is not available.

There is nothing else you need to do, except set the date and message etc. Go to Menu > Tools > Automatic Replies.