Dear Huseyin ALP, OWA is very simple thing. The most common problem is connected to authentication issue. Check auth config in Exchange>protocols>HTTP and in your IIS>webmail. If you have a firewall in front of exchange's IIS you cannot use Integrated auth. Set auth for Exchweb to Anonymous and Basic. In basic field type \domainname, so your users will not need to type domain name when authenticated. For Exchange and Public set only basic authentication with \domainame. For Exchadmin set Integrated for security purposes. Check subfolders in IIS for authentication as they all should inherit parent settings. Leave Host Header Name blank. In Home Directory of your webmail check A redirection to a URL: and type \Exchange, and put check mark in A directory below this one. Regarding IIS Lockdown tool, check if you enabled: HTTP,SMTP,NNTP,.asp,.htr. Do not disable WebDAV. If still have a problem send me all errors from app log. Cheers