PHPMailer\PHPMailer

SMTP::quit() │ public │ WP 1.0

Send an SMTP QUIT command. Closes the socket if there is no error or the $close_on_error argument is true. Implements from RFC 821: QUIT <CRLF>.

Method of the class: SMTP{}

No Hooks.

Return

true|false.

Usage

$SMTP = new SMTP();
$SMTP->quit( $close_on_error );
$close_on_error(true|false)
Should the connection close if an error occurs?
Default: true

SMTP::quit() code WP 6.6.2

wp-includes/PHPMailer/SMTP.php 
public function quit($close_on_error = true)
{
    $noerror = $this->sendCommand('QUIT', 'QUIT', 221);
    $err = $this->error; //Save any error
    if ($noerror || $close_on_error) {
        $this->close();
        $this->error = $err; //Restore any error from the quit command
    }

    return $noerror;
}