( FIXED )
With the release of Web Mail 5.16.3 we have found a bug that only affects users of Internet Explorer 5.5 or older.
We still try to fully support IE 5.5, but be aware that we no longer test or support IE 5.0. If you are using IE 5.5 you may have a problem with buttons not being visible, including the "Sign In" button on the login page. This will be fixed soon. I apologize for the inconvenience.
If you are using an operating system that can take the upgrade to IE 6.0, that will fix the problem too. And if you can run Firefox or Netscape (at least temporarily), those browsers do not have the problem.