called on event trigger, for example form submit. import {fetch} from 'wix-fetch'; export function sendWithService(key, sender, recipient, subject, body) { const url = "https://api.sendgrid.com/api/mail.send.json"; const headers = { "Authorization": "Bearer " + key, "Content-Type": "application/x-www-form-urlencoded" }; let data = `from=${sender}&to=${recipient}&subject=${subject}&text=${body}`; console.log("in backend code, data = " + data) let request = { "method": "post", "headers": headers, "body": data }; return fetch(url, request) .then(response => { console.log("back from send grid"); response.json() }); }