Found the answer on the MS website...here's the procedure:
You can use the Rules Wizard to automatically send reply messages to certain people even when you're not running Outlook. So, when you're on vacation and your computer is turned off, you can still send custom replies to messages from certain people. Here's how to have Exchange Server do this automatically.
Create a rule to have Exchange Server send an automatic reply
On the Tools menu, click Rules Wizard.
In the Apply changes to this folder list, click the Inbox you want to create the rule for.
Click New, Click Start from a blank rule.
Click Check messages when they arrive, and then click Next.
In the Which condition(s) do you want to check list, select the From people or distribution list check box.
In the Rule description list, click the underlined phrase, people or distribution list.
In the Type name or select from list box, type the name of each person you want to receive the custom reply, and click From after you type each name.
Click OK, and then click Next.
In the What do you want to do with the message list, select the Have server reply using a specific message check box.
In the Rule description list, click the underlined phrase, a specific message.
In the subject line and message body, type whatever information you'd like to appear in your custom reply.
Click Close, and when prompted to save changes, click Yes.
Click Next, and select the check box next to any exception that you want.
Click Next, and in the Please specify a name for this rule box, type a name for the rule.
Click Finish, and then click OK.
That's it. Now, when you receive a message from one of the people you specified in step 8, they'll automatically receive your custom response.
