When a user is out of the office and has time sensitive customer corespondence you can configure the Out of Office Assistant to forward emails to another user.
Open the OOA by going to Tools> Out Of Office Assistant
Click on the Rules button at the bottom of the OOA.
Click Add Rule.
1. Check the Forward box.
2. Click the To... button.
This will open the Address book and you may select the users to whom you wish to forward emails when out of the office.
3. Click the OK button.
Enable the option to Send out of office replies. If you do not wish to have a message sent leave the body of the message blank.