If you try to log into a new install and you receive this error:

An error occurred during a connection to xxx.xxx.xxx.xxx:10000.
SSL received a record that exceeded the maximum permissible length.
(Error code: ssl_error_rx_record_too_long)

It is because SSL is not configured for Webmin and it must be enabled.

Connect to the URL without the s (http: not https:).

Log in to Webmin and enable/install SSL.