if you have a smtp server that is allowing the traffic from the wr31 when you setup the smtp server in the configuration you just dont enter username / password
if this is a normal port 25 connection you should be able to use the analyser on the wan interface and filter on port 25 to see the negotiations and flow of the outbound email.
you can force and email out using the email command in cli
Format "EMAIL <TO> <FROM> <SUBJECT> <TEMPLATE> [ATTACHMENT LIST]"
hope that is some help