Using JScript, you need to make sure that your string for your path is more like
"C:\\temp\\MyResults.mht"
As the backslash character is a special character.
As for MAPI... this is essentially, if you go to Windows Control Panel and select the Mail icon, the protocols (SMTP, MS Exchange, etc) configured there is what TC uses for sending mail. In other words, you need to have an e-mail client of some sort set up on your workstation to use BuiltIn.SendMail and the credentials of that email client are what are used to actually send the mail.