Your best bet would be to use the first method of
sendEmail(recipient, subject, body, options)
This method can take all of your parameters. You pass all of your parameters in the options part.
It will look something like this.
var file = DriveApp.getFileById('12345mnopqrstuvwxyz');
var blob = Utilities.newBlob('HTML content here',
'text/html',
'my_email.html');
MailApp.sendEmail('mike@example.com',
'Attachment example',
'Two files are attached.',
{
attachments: [file.getAs(MimeType.PDF), blob],
replyTo: 'ReplyTo@Email.com'
});
here is a screenshot of the documentation

Google documentation here