How to disable webmail client auto-loading feature
If it was enabled with a reasonable timeout, you can disable it by clicking Stop in the on-page “pop-up” box which should appear in the bottom part of the front page.
If the timeout was set to 1 second or 2 and redirection is made too fast, you can click the back button of the browser to access the front-page and click [Disable autoload].
(Tested and working on IE9 and Chrome)
Simple as that.