We can send files to any other person or organization as attachment. Only if one download and opens it, will know if the file is correct or not, that too if it is in human readable format, like pdf, doc, excel etc. What if it is binary file or image, which is to be given to the other person? The other person cannot identify it until it uses it in the application for which it is intended.
One easy way is to do CRC32 check at both the ends. There is one free tool available hashtab which does hash calculation and generates the unique values.You can download the hashtab from below link and try it.
http://www.implbits.com/HashTab/HashTabWindows.aspx
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