wp-includes/ms-functions.php:2278Corrects From host on outgoing mail to match the site domain.
$phpmailerPHPMailerfunction fix_phpmailer_messageid( $phpmailer ) { $phpmailer->Hostname = get_network()->domain;}Introduced in MU (3.0.0). One change between 6.7.7 and 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
$phpmailer retyped from PHPMailer to PHPMailer\PHPMailer\PHPMailer.verified against sourcesrc/wp-includes/ms-functions.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.