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Hi Narendra, If you take another look at the ADM documentation, specifically the "Response Format" section of Sending Messages (at https://developer.amazon.com/sdk/adm/sending-message.html#ResponseFormat ), you will see that for status code 500, no reason is meant to be provided. In general, 500 status refers to an "Internal Error" meaning there is nothing wrong with your request that Amazon can recognize, but it still failed. However, it is strange that you are getting a "retryAfter" field since that same documentation says "retryAfter" is only in the response for 429 and 503. This suggests a bug on Amazon's side to look into.

Narendra, Can you tell us Formatted HTTPS connection for the POST request and JSON representation of the message. So that we can re-create the scenario to debug the issue. I'm doing the ideal way and followed the example which is working fine. However your request for Description of 500 more than just "There was an internal server error" is taken.