BCC site admin email on all Event Tickets' RSVP ticket emails so they get a copy of it too

functions.php

<?php
/**
  * BCC site admin email on all Event Tickets' RSVP ticket emails so they get a copy of it too
  *
  * From https://gist.github.com/cliffordp/4f06f95dbff364242cf54a3b5271b182
  *
  * Reference: https://developer.wordpress.org/reference/functions/wp_mail/#using-headers-to-set-from-cc-and-bcc-parameters
  *
  */
function cliff_et_rsvp_bcc_admin_ticket() {
	// get site admin's email
	$bcc = sanitize_email( get_option( 'admin_email' ) );
	
	// set Headers to Event Tickets' default
	$headers = array( 'Content-type: text/html' );
	
	// add BCC email if it's a valid email address
	if ( is_email( $bcc ) ) {
		$headers[] = sprintf( 'Bcc: %s', $bcc );
	}
	
	return $headers;
}
add_filter( 'tribe_rsvp_email_headers', 'cliff_et_rsvp_bcc_admin_ticket' );