If you can`t replay to received emails for some day, this is better to use Outlook Auto replay tools.
For this, first write a text for your mail and save it on your HDD.
Then go to Tools menu and select "Mail" from "Message Rules" submenu.
Now, Tick " For all messages " from " Select the Conditions for your rules" and " Reply with messages" from " Select the Action for your rule" .
Finaly click on "Message" from " Rule Description" and select your saved message.

A better way to do this would be to set the mail server (instead the computer running the Outlook) to send the messages. This is usually called as "Vacation Message".

This of course requires that your email service provider offers such service. I'm not sure about the rest of the world, but here in Finland my experience that most ISP's have this option at least for a small extra fee. For companies, a vacation message is often a neccessity. Having customer to wait a reply for a 4 week holiday doesn't sound like good service. Instead a nice, and most importantly, instant, message describing the situation and advising the customer to contact another email for urgent issues might mean the difference between losing and not losing a customer.

CommuniGate Pro, which my university uses as a mail management system has this option under 'Rules'. I am not sure if the cPanel here at asta has such options, at the moment I can't get logged in.

EDIT:

I finalyl got into cPanel and there is an AutoResponder tool like I remembered. Right there in the first row.