If you are getting an error that says “File cannot be found” or if you are receiving a 404 error when you try to go to webmail.mydomain.com, this is due to the fact that default mapping application extensions do not include php support.To solve this, do the following:
1. Go to “Start” – > “Administrative Tools” -> “Internet Information Services (IIS) Manager”
2. Expand the server (local computer)
3. Expand “Web Sites”
4. Right-click on “webmail(default)” and click “Properties”
5. Go to the “Home Directory” tab
6. Click on the “Configuration” button towards the bottom.
7. In the list box that appears, if the extensions php, php3, and phtml do not exist, you have found your problem.
8. Click “Add”
9. Type the location of the file php.exe in the “Executable” field. For example: C:\Program Files\SWsoft\Plesk\Php\php.exe
10. Type: .php in the “extension” field.
11. Leave everything else as default checked. Click “OK”.
12. Repeat this setup using the same executable and adding the extensions: .php3 and .phtml
13. Exit out of everything. Webmail should be up and running now.