You want to have really secure mail account? You need to use 2-step verification process with cell phone as token. Google's GMail makes this very easy - just go to Security Settings of your Google account and enable it. On next login you will have to provide password along with special code sent to you by SMS.
Next thing that needs to be done is to allow Kadu to access your GTalk. 2-step verification can not be used, as Kadu has only one field for entering password. You need to create special application password just for it. Go back to Security Settings, click on Setting next to 2-step verification and select Manage application-specific password. Enter "Kadu" as application name, click "Generate Password". Enter this created password into Kadu's Account settings and you are done.