Webmail on Windows not loading and eventually timing out

Please check to make sure that IIS for webmail is set to parse PHP pages in CGI mode as it will n
ot work with PHP in ISAPI mode.

To verify PHP is running in CGI for webmail go to:
IIS Manager -> Websites -> webmail -> properties.

Select the home directory tab -> Configuration -> Application mappings, ensure that the extension
.php is being handled by the executable version of PHP which is in
"C:\Program Files\SWsoft\Plesk\Additional\Php\php.exe"