PHPMailer\PHPMailer

SMTP::hello() │ public │ WP 1.0

Send an SMTP HELO or EHLO command. Used to identify the sending server to the receiving server. This makes sure that client and server are in a known state. Implements RFC 821: HELO <SP> <domain> <CRLF> and RFC 2821 EHLO.

Method of the class: SMTP{}

No Hooks.

Return

true|false.

Usage

$SMTP = new SMTP();
$SMTP->hello( $host );
$host(string)
The host name or IP to connect to
Default: ''

SMTP::hello() code WP 6.6.2

wp-includes/PHPMailer/SMTP.php 
public function hello($host = '')
{
    //Try extended hello first (RFC 2821)
    if ($this->sendHello('EHLO', $host)) {
        return true;
    }

    //Some servers shut down the SMTP service here (RFC 5321)
    if (substr($this->helo_rply, 0, 3) == '421') {
        return false;
    }

    return $this->sendHello('HELO', $host);
}