I'm wondering if you are using Outlook in Corporate mode or Internet mode? Are you wanting to implement this just for yourself or enterprise-wide?
You may want to check out a product called Email Templates that you can use to prepare specific templates for certain emails, including scripting options. Its at www.emailtemplates.com They have a lot of features that might assist.
If you are also concerned about using the right signature and "From" address, you can check out RightFrom COM Add-in which automates the filling of the "From" field based on current mailbox name. I.e., "if you're replying the message that sits in Inbox folder of Sales mailbox, it's sender name will be Sales, and then you forward message that sits in Inbox folder of Info mailbox the sender become Info."
kdrungilas, www.outsourcecorp.com