Error: LiveId authentication code has returned error 0x8004920a, indicating that there is a problem with your server configuration. Please check the Application Event Log for detailed information and correct the problem.
SUmail Users report they are unable to login to SUmail, typically when connecting with Mac Safari or Firefox. They report getting the error message shown above.
Per the Microsoft Live forum, the problem is attributed to invalid browser cookies. Removal of the offending cookies (or deletion of all browser cookies) typically resolves the problem.