Easy Digital Downloads + EDD Commissions extension - Include the customer's email address for the vendor in the email

gistfile1.php

<?php

function sumobi_edd_commissions_email_alert( $user_id, $commission_amount, $rate, $download_id, $commission_id, $payment_id ) {
	global $edd_options;

	/* send an email alert of the sale */
	$from_name = isset( $edd_options['from_name'] ) ? $edd_options['from_name'] : get_bloginfo( 'name' );
	$user      = get_userdata( $user_id );
	$email     = $user->user_email; // set address here

	// get customer information
	$user_info = edd_get_payment_meta_user_info( $payment_id );

	// customer's email address
	$customer_email_address = $user_info['email'];

	// subject
	$subject   = __( 'New Sale!', 'eddc' );
	$message   = __( 'Hello', 'eddc' ) . "\n\n" . sprintf( __( 'You have made a new sale on %s!', 'eddc' ), stripslashes_deep( html_entity_decode( $from_name, ENT_COMPAT, 'UTF-8' ) ) ) . ".\n\n";
	$variation = get_post_meta( $commission_id, '_edd_commission_download_variation', true );
	
	// email message
	$message  .= __( 'Item sold: ', 'eddc' ) . get_the_title( $download_id ) . ( ! empty( $variation ) ? ' - ' . $variation : '' ) . "\n\n";
	$message  .= __( 'Amount: ', 'eddc' ) . " " . html_entity_decode( edd_currency_filter( edd_format_amount( $commission_amount ) ) ) . "\n\n";
	$message  .= __( 'Commission Rate: ', 'eddc' ) . $rate . "%\n\n";
	$message  .= __( 'Customer\'s Email Address: ', 'eddc' ) . $customer_email_address . "\n\n";
	$message  .= __( 'Thank you', 'eddc' );
	$message   = apply_filters( 'eddc_sale_alert_email', $message, $user_id, $commission_amount, $rate, $download_id );

	if ( class_exists( 'EDD_Emails' ) ) {

		EDD()->emails->__set( 'heading', $subject );
		EDD()->emails->send( $email, $subject, $message );

	} else {

		$from_name = apply_filters( 'eddc_email_from_name', $from_name, $user_id, $commission_amount, $rate, $download_id );

		$from_email = isset( $edd_options['from_email'] ) ? $edd_options['from_email'] : get_option( 'admin_email' );
		$from_email = apply_filters( 'eddc_email_from_email', $from_email, $user_id, $commission_amount, $rate, $download_id );

		$headers = "From: " . stripslashes_deep( html_entity_decode( $from_name, ENT_COMPAT, 'UTF-8' ) ) . " <$from_email>\r\n";

		wp_mail( $email, $subject, $message, $headers );

	}
}
remove_action( 'eddc_insert_commission', 'eddc_email_alert', 10, 6 );
add_action( 'eddc_insert_commission', 'sumobi_edd_commissions_email_alert', 10, 6 );