The Out-of-Office Assistant is only available to those Outlook users who
connect to an Exchange server for email. This is normally found in a business
environment and that type of mail account is called an Exchange account. The
Out-of-Office Assistant is enabled once you are connected to an Exchange
server with the correct account.
If you are a home user, this type of out of office reply is not available
but you do have options. You can check your ISP to see if they have a webmail
function, you may be able to set up an auto-reply there OR you can set up a
rule. For details on this rule, read here:
http://www.howto-outlook.com/faq/oooa.htm
Hope you find this helpful.