Hello,
On our setup the url,
https://mail01.xxx.com/WebDAV/ prompts for user/password and then if I login with a mailbox creditentials, it returns "bad request". I guess it's correct because it needs probably to be a POST instead of a GET request.
Does it asks you for a password on your setup ?
Are you sure that in your IIS the port 80 for the hostname you're using is bound to the correct IIS virtual host (SmarterMail?).
Kind regards.
Sébastien Riccio
System & Network Admin
https://swisscenter.com