I am glad that you liked “Forgot Password Script”. The $resetmailmesshtml = ” sets a custom message in html format. so between the inverted comma you will put the custom reset mail message.
there is no option to chose between html or plain text mail. the sendMail method in includes/class.recoverpas.php sets the mail for plaintext and html format if you would like to tweak it a bit or replace with another method to send mail.
Both html and paintext messages are set and depending on the mail client preferences either one of two is shown currently.