You can set up a rule for incoming messages using TOOLS> Rules and Alerts>.
Add a new rule that responds to all incoming mail with the text you enter.
Toggle on and off whenever you come and go...
Not as cool, but hey it works.
-FT
It won't be unless you use MS Exchange for your mail server. Otherwise,
define a rule to reply to inbound e-mails. Go do a search at
Microsoft's support knowledgebase site (http://support.microsoft.com)
and search on "emulate out of office".