A "run a script" rule action runs not an external script but a VBA procedure with a MailItem or MeetingItem as its parameter. That item is processed by the code, as in this example:
Sub RunAScriptRuleRoutine(MyMail As MailItem)
Dim strID As String
Dim olNS As Outlook.NameSpace
Dim msg As Outlook.MailItem
Dim rply as Outlook.MailItem
strID = MyMail.EntryID
Set olNS = Application.Session
Set msg = olNS.GetItemFromID(strID)
' do stuff with msg, e.g.
Set rply = msg.Reply
rply.Body = "What you want the reply to say."
rply.To = "(e-mail address removed); (e-mail address removed)"
rply.Send
Set msg = Nothing
Set rply = Nothing
Set olNS = Nothing
End Sub
For Outlook VBA basics, see
http://outlookcode.com/article.aspx?id=49ww.outlookcode.com/d/code/zaphtml.htm#ol2002 for another example.