Nodemailer HTML not working with sendgrid

I am using sendgrid and nodemailer trying to send an HTML email. here is the code:

for(var i = 0;i<emails.length; i++){
    email.sendMail({
        from:'"Name" <noreply@domain.com>',
        to:emails[i],
        HTML:"<h1>hi</h1>",
        generateTextFromHTML:true,
        subject: "Blah"
    },function(err,res){
        if(err){console.log(err)};
        if(res){console.log(res.message)};
    })
}

let me know if you need anymore information let me know. thanks, ari