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I have a Windows Server 2008 r2 installation with configured FTP and IIS.

If I upload through FTP two files: "test.txt" and "" and then try to access these files through HTTP, then I can access only test.txt - then trying to access results in 404.

I found this link: File Name Extensions

I followed the instructions to edit the Request Filtering. And denying works - if I set to deny ".txt" extension, then trying to access test.txt results in the same 404 error. But I don't manage to allow ".abc", adding it as allowed extension doesn't seem to have any effect.

Is there some other place where I need to make changes too in order to be able to access the file through HTTP? If I uninstall "Request Filtering", will then all files be accessible through HTTP?

Now I removed Request Filtering altogether and rebooted the server - but without change - accessing the ".abc" file still gives 404. I'm connecting to this server through a VPN tunnel. Is it possible that VPN filters out such requests and returns 404 instead?

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up vote 1 down vote accepted

You were close, but not quite right. IIS will respond with 404 for any file that doesn't have a registered MIME Type. Here's how to fix it:

  • Open IIS Manager
  • Select the Server, Site, or Application that you want to add the mime type to
  • In the IIS sub-section, open the MIME Types feature
  • Add the extension for your ".abc" file with an appropriate mime type (for whatever type of file it actually is).

Here is the relevant documentation:

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perfect - that did do the trick :) thanks a lot! – Mat Sep 11 '12 at 20:28

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