This sporadically happens for some AWS accounts, it's not because of your settings but because some weird behavior in amazons end.Unable to determine service/operation name to be authorized
You don't. Mailwizz uses Amazon SDK to send along the data to the amazon servers, so that SDK does all the job.Btw.. how do we add the header for Content-Type?? as in Content-type: application/x-www-form-urlencoded