I trust you have browsed through Sue Mosher's page Automatic Message Processing Tools site http://www.slipstick.com/addins/auto.htm#tools?
If you run just Outlook, not a server based system, your options are limited.
A quote from http://support.microsoft.com/?kbid=290654, "Microsoft Outlook does not provide built-in functionality that allows you to send mail or perform some other custom task at a specific time interval."
You cannot launch the Outlook document object model from a service on NT or W2K either. Outlook and Office are not designed to be used as servers, they need an active user profile - more details from http://support.microsoft.com/kb/257757.
However, if you are handy with VBA, you could develop your own routine following the advice in http://support.microsoft.com/kb/209948/EN-US/ "How to use Automation to send a Microsoft Outlook message using Access 2000".
Developing a program in VB6 and using vbSendMail.dll may be exactly what you need: http://www.freevbcode.com/ShowCode.Asp?ID=109