Below is something i send to a client a couple of months ago. Hope I've got all the steps here!  It's certainly not as easy as in OE.

First, you have to create your reply message in Word and save it as a .txt file.  You will be ask to retrieve this file later on.

Click on Tools/Message Rules/Mail
If you have no message rules, you are taken to the New Rules Dialog window
There are 4 sections.
Section 1 – scroll to the bottom and click on the white box to the left of For All Messages – a check mark will appear
Section 2 – scroll to Reply with Message and click the white box to the left to set a check mark
Section 3 – click on the underlined word “message” – now you get the Open dialog box
At the bottom beside Files of Type – click on the arrow to the right of the box to select Text (.txt)
Then open the message you created earlier
Section 4 – give the rule a name
Click OK

At this point the rule is active – to turn it on or off:
Again click on tools/message rules/mail
This time you get the Message Rules dialog box and the message you created should be there with a check mark in the white box to the left
Click on the white box to remove the check mark
The Rule Description box will say This Rule is Currently Turned Off
To activate the message turn the check mark on

Note – if you want to change the message (e.g. with dates or whatever), just change change it   - you don’t have to do anything else if you keep the same file name  because the rule points to the file, the message isn’t imbedded in the rule

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