With content type “x-www-form-url-encoded” as the name indicates both the keys and values are URL encoded. So with curl you would actually get something like this.
curl --location --request POST "https://some-target-url.com" --header "Content-Type: x-www-form-url-encoded" --data="email=myemail%40domain.com"
In mendix you could use a ‘post’ REST action as described in this forum post below. Just make sure you don’t forget to URL encode the keys and values before adding it to the request body.
https://forum.mendix.com/link/questions/89477
The error code is:
422 Unprocessable Entity
The server understands the content type of the request entity (hence a 415 Unsupported Media Type status code is inappropriate), and the syntax of the request entity is correct (thus a 400 Bad Request status code is inappropriate) but was unable to process the contained instructions.
For example, this error condition may occur if an XML request body contains well-formed (i.e., syntactically correct), but semantically erroneous, XML instructions.
Could it be something so simple that you really tried to supply myemail@domain.com instead or your own mail adres?
Otherwise check the other side why your mail address is not accepted.
Regards,
Ronald