mail(): Policy restriction in effect. The fifth parameter is disabled on this system.

[MircoBabin]

// PHP mail() statement
mail(
    $to,
    $subject,
    $message,
    $additional_headers = [],
    $additional_params = ""
)

My hosting provider has activated some policy, that the Php mail() function must not be called with 5 parameters. Effectively disallowing $additional_params. When providing a 5th parameter a Php warning mail(): Policy restriction in effect. The fifth parameter is disabled on this system. is issued.

The function send() uses the mail() statement.

    // OLD
    public function send()
    {
        $to = $this->getToForSend();
        $headers = $this->getHeadersForSend();

        if (empty($to)) {
            throw new \RuntimeException(
                'Unable to send, no To address has been set.'
            );
        }

        if ($this->hasAttachments()) {
            $message  = $this->assembleAttachmentBody();
            $headers .= PHP_EOL . $this->assembleAttachmentHeaders();
        } else {
            $message = $this->getWrapMessage();
        }

        return mail($to, $this->_subject, $message, $headers, $this->_params);
    }

Changing this to below solves the warning.

    // CHANGED
    public function send()
    {
        $to = $this->getToForSend();
        $headers = $this->getHeadersForSend();

        if (empty($to)) {
            throw new \RuntimeException(
                'Unable to send, no To address has been set.'
            );
        }

        if ($this->hasAttachments()) {
            $message  = $this->assembleAttachmentBody();
            $headers .= PHP_EOL . $this->assembleAttachmentHeaders();
        } else {
            $message = $this->getWrapMessage();
        }

        if ($this->_params !== null) {
            return mail($to, $this->_subject, $message, $headers, $this->_params);
        } else {
            return mail($to, $this->_subject, $message, $headers);
        }
    }

P.S. Sorry, I am unable to provide a PR.