Pop\Mail\Mail::setParams PHP Method

    public function setParams($params = null)
    {
        if (null === $params) {
            $this->params = null;
        } else {
            if (is_array($params)) {
                foreach ($params as $value) {
                    $this->params .= $value;
                }
            } else {
                $this->params .= $params;
            }
        }
        return $this;
    }

 public function testSetAndGetHeaders()
 {
     $m = new Mail();
     $m->setHeader('X-Reply-To', '*****@*****.**');
     $m->setHeader('X-Reply-To', 'Bob <*****@*****.**>');
     $m->replyTo('*****@*****.**');
     $m->setHeaders(array('Reply' => '*****@*****.**'));
     $m->setParams(' -i');
     $m->setParams(array(' -t'));
     $m->setParams();
     $this->assertEquals('*****@*****.**', $m->getHeader('Reply-To'));
     $this->assertEquals(4, count($m->getHeaders()));
 }