What I'm looking for is a way to access the mail box. "KONtx.dialogs.YahooLogin" allows to be connected, but I don't know what functions or API I can use to access the mails ...
If someone has an idea about this, it would be very helpful
Currently there isn't support for access Yahoo! Mail data directly from within a widget. You would need to write a backend service which authenticates the user using BBAuth using the normal published APIs on developer.yahoo.com and then have a way to authenticate users from your widget with your own backend service.