How to Modify Entourage Contact Email Address

I’ve tried the following and receive an “Expected a Reference” error. What is the proper syntax for modifying a contacts’ email address? I’ve also tried “set default email address of first contact to …”

tell application “Microsoft Entourage”
set email_address to “user@domain.com”
tell first contact to set its default email address to email_address
end tell

set contents of default email address of first contact to email_address

“default email address” is a reference to the class “email address”, which has both “contents” and “label”.