Send Email API Error 500

Send Email API Error 500

Hi,

I'm trying to test the Send Email API using Postman

The URL is 

Header Info
Authorization: <my authorization token>

Body - Raw(JSON)

{
    "fromAddress": "my email address",
    "toAddress": "my gmail address",
    "subject": "Email - Always and Forever",
    "content": "Email can never be dead. The most neutral and effective way, that can be used for one to many and two way communication."

}

Yet I get the following error:
 "status": {
        "code": 500,
        "description": "Internal Error"
    },
    "data": {}

- When I try to use PHP CURL:
[2, {"msg":"Error while processing!","status":"500"}]
Help please!!
Thanks.