(EDİT: BOUNTY ADDED) Amazon APIs, issues with uploading a file

Edit: I added 100 point bount on stackoverflow.

Trying to upload a product feed to Amazon. Using postman it is giving me the following error:

To check if file is uploaded without modifications on the way, I calculate MD5 value of the file submit to amazon. Then it says

“the Content-MD5 HTTP header you passed for your feed did not match the Content-MD5 we calculated for your feed”

I checked the values and saw that I am generating the MD5 same with amazon in amazon’s online test environment.

So the problem is possibly the way I upload the file, maybe I am not posting the file correct way, so that amazon can’t find the file and can’t calculate the same MD5 with me.

This is what I do

I put contents of file into file.xml in my desktop. And below are my settings.

Headers: Content-Type: text/xml
Body: form-data, Key: File, Value: file.xml

Do you think this is enough ? Is there something I am missing ?