SMTP connection is not possible without encryption.

[IgorA100]

This is because by default PHPMailer.php has TLS encryption enabled.
If the SMTP server does not support encryption, it is not possible to connect to it.

    /**
     * Whether to enable TLS encryption automatically if a server supports it,
     * even if `SMTPSecure` is not set to 'tls'.
     * Be aware that in PHP >= 5.6 this requires that the server's certificates are valid.
     *
     * @var bool
     */
    public $SMTPAutoTLS = true;

If encryption is not specified in the SMTP settings, then SMTPAutoTLS should be disabled
Solution:
In the file "\app\Mailer.php" change the code:

BEFORE:

		$this->mailer->SMTPSecure = $this->smtp['secure'];
		$this->mailer->SMTPAuth = (bool) $this->smtp['authentication'];

AFTER:

		$this->mailer->SMTPSecure = $this->smtp['secure'];
		if (!$this->smtp['secure']) {
			$this->mailer->SMTPAutoTLS = false;
		}
		$this->mailer->SMTPAuth = (bool) $this->smtp['authentication'];