I would like to insert the tracking number from each invoice into an email template. Does anyone know what the variable name is for the tracking number?

For that matter, how do I get the proper fields names for the various fields in the databases?

When in the email template editor, if you look towards the top of the screen you'll see a couple of pull-down menus: "Insert Invoice Field" and "Insert Auction Lot Field".
These menus contain all of the variables you can use in your emails - including tracking#.

Hope that helps!
Rich