Follow Up Email after Appt. Completed

I found the below code and I have gotten it to work on a test site. My question is in the message area is there a way to get html formatting to be accepted? I have it turned on for the plugin as I use it for the confirmation and reminder emails.

Ultimately I'd like to send a link to our feedback form for the customer to fill out after their appointment.

function follow_up( $value ) {
global $wpdb, $appointments;

$a = $appointments;
// Double check if A+ is active
if ( !is_object( $a ) )
return;

// Follow up time in hours
$hour = 24;
// Follow up email subject
$subject = 'Follow up subject';
// Follow up email message
$message = 'Follow up message';

$results = $wpdb->get_results( "SELECT * FROM " . $a->app_table . " WHERE note NOT LIKE '%Follow up sent%' AND status='completed' AND DATE_ADD(start, INTERVAL ".$hour." HOUR) <'" . date ("Y-m-d H:i:s", $a->local_time ). "' " );
if ( $results ) {
foreach ( $results as $r ) {
// Send email
if ( wp_mail( $r->email, $subject, $message, $a->message_headers() ) ) {
// Save so that we don't send email again
$wpdb->update ( $a->app_table,
array( 'note' => $r->note . ' Follow up sent' ),
array( 'ID' => $r->ID ),
array ( '%s' )
);
}
}
}
}
add_action( 'update_option_app_last_update', 'follow_up' );

Thank you!!
~Suzy

Correction edit: I put code from different post I'm using the one that is now posted sorry!
Follow up emails for A+