RPM API Key by Header Only
Originally the RPM API required the API key to be passed in a "Key" property in the API request body. In early 2015 we allowed the key to be passed as an RpmApiKey header and promoted that as the preferred way to pass the key. In the next version of RPM we will no longer support the old method of passing the key in the body.
From what we can see everyone is using the header anyway, so this email is just a friendly reminder and you shouldn't need to change anything. If you are unsure you can check your API history and you will see in the request history if you are passing the key in the body.