Based on information you provided, looks like JSON you are trying to submit isn't properly formatted. At least what server reply means.

>
>I wrote a routine to POST a file and some additional information to a server. When sending the POST I get an error 500 with the following response:
>"{"fault":{"faultstring":"JSONThreatProtection[ValidateJsonMessage]: Execution failed. reason: Expecting : at line 1","detail":{"errorcode":"steps.jsonthreatprotection.ExecutionFailed"}}}".
>
>I understand, that there is a server error. But I wonder if someone can explain the response to me. This is my first try of a POST. So I may do something wrong here.
>
>Please help.
>
>TIA
>Gerhard Schmidbauer