Access-Control-Allow-Headers Error

I am getting the following error when attempting to do a POST.

Failed to load https://my.api.mockaroo.com/emailforms.json?key=********&__method=POST: Request header field Content-Type is not allowed by Access-Control-Allow-Headers in preflight response.

Is there anything I can do to prevent this from happening? According to https://stackoverflow.com/a/25727411/8627019 this is a server side issue.