PHPMailer\PHPMailer\PHPMailer::addAnAddress PHP Method

    protected function addAnAddress($kind, $address, $name = '')
    {
        if (!in_array($kind, ['to', 'cc', 'bcc', 'Reply-To'])) {
            $error_message = $this->lang('Invalid recipient kind: ') . $kind;
            $this->setError($error_message);
            $this->edebug($error_message);
            if ($this->exceptions) {
                throw new Exception($error_message);
            }
            return false;
        }
        if (!$this->validateAddress($address)) {
            $error_message = $this->lang('invalid_address') . " (addAnAddress {$kind}): {$address}";
            $this->setError($error_message);
            $this->edebug($error_message);
            if ($this->exceptions) {
                throw new Exception($error_message);
            }
            return false;
        }
        if ('Reply-To' != $kind) {
            if (!array_key_exists(strtolower($address), $this->all_recipients)) {
                array_push($this->{$kind}, [$address, $name]);
                $this->all_recipients[strtolower($address)] = true;
                return true;
            }
        } else {
            if (!array_key_exists(strtolower($address), $this->ReplyTo)) {
                $this->ReplyTo[strtolower($address)] = [$address, $name];
                return true;
            }
        }
        return false;
    }