fix_phpmailer_messageid() │ WP 3.0.0

Corrects From host on outgoing mail to match the site domain.

No Hooks.

Returns

null. Nothing (null).

Usage

fix_phpmailer_messageid( $phpmailer );
$phpmailer(PHPMailer\PHPMailer\PHPMailer) (required)
The PHPMailer instance (passed by reference).

Changelog

Since 3.0.0 Introduced.

fix_phpmailer_messageid() code WP 6.9.1

wp-includes/ms-functions.php 
function fix_phpmailer_messageid( $phpmailer ) {
	$phpmailer->Hostname = get_network()->domain;
}