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function is not described

PHPMailer\PHPMailer

PHPMailer::getLastMessageID() public WP 1.0

Return the Message-ID header of the last email. Technically this is the value from the last time the headers were created, but it's also the message ID of the last sent message except in pathological cases.

{} It's a method of the class: PHPMailer{}

No Hooks.

Return

String.

Usage

$PHPMailer = new PHPMailer();
$PHPMailer->getLastMessageID();

Code of PHPMailer::getLastMessageID() WP 5.7.2

<?php
public function getLastMessageID()
{
    return $this->lastMessageID;
}