Only corporate emails validation for Contact Form 7

you could try

let provider = ["gmail","hotmail","yahoo"];
let mail = document.getElementById("email_field");
let btn = document.getElementsByClassName("send_btn")[0];
provider.forEach(e =>{
if(mail.value.includes(e)){
    console.log("true");
    btn.disabled=true;}
});

Hey, parsec1, alternatively, you could also implement validation via PHP filters:

https://contactform7.com/2015/03/28/custom-validation/