I have installed RoundCube under IIS (Windows XP German) and am running MySQL and PHP on the same system. I have got the problem that when I open the login page (http://localhost/mail.index.php), type in the correct user information and then press the Login button it just gives me the page for "HTTP 405 - Resource not allowed".

I think that it has to do with the way IIS reacts the the action field that is provided in the login form:

If I save the html source and replace the action field above with 'action="index.php"' the list of messages turns up. I myself did some PHP/MySQL development but don't have a clue what the problem here is. I think that I should get further if RoundCube would not only provider "./" in den login field but also the complete address of the file. I don't really know if it would solve the problem but at least the login should work - so I think - if RoundCube would use 'action=\"" . $_SERVER["PHP_SELF"]'.