How to get user name and password for session that requires SMTPAuthentication

[james_mail]

Hi,
I am developing Mail Relay application,i uses Server JAMES for relay.
I have a Gmail's account.
I used Mail Client to send a message to JAMES.Then JAMES relay to Gmail,but 
Gmail requires authentication username and password.
How to get username and password from JAMES relay to mail to Gmail.

Thanks!!!!!