Their is no way to set the SMTP password with a property in JavaMail:
http://java.sun.com/products/javamail/javadocs/com/sun/mail/smtp/package-summary.html

"To use SMTP authentication you'll need to set the |mail.smtp.auth| property
(see below) and provide the SMTP Transport with a username and password when
connecting to the SMTP server."

So you must give the SMTP Transport at least the password.