Hi Kunal,
For this one we would need to see a fiddler or wire shark trace to understand what its tryin to get to that it is not able to. I know you mentioned that you dont have anything like that installed on the machine, but I dont think we can troubleshoot this further without having a way to see this. You can try using F12 (dev tools), and look at the network tab to try and see if it shows you anything. You would go to upload an attachment, but before you click the upload button after selecting a file, you would hit F12 to show the dev tools, then you can hit the upload button and it may show you what its trying to access that it cant.
Aside from that, have you tested on Windows 10 with another browser such as Chrome or FireFox just to see if its something specific to IE?
Additionally, does this happen on both uploads and downloads? Or just uploads?
Let us know what you find.
Thanks,
Jon I.