Why does the site block IP when parsing?

Question

Python

Need to scrap the site

def get_html(url):
    request = urllib.request.Request(url)
    request.add_header('User-Agent', 'Mozilla/5.0 (Windows; U; Windows NT 5.1; ru; rv:1.9.1.3) Gecko/20190824 Firefox/3.5.3')

    cookies = [
        ['cookie', '__unam=4145b67-1586e230cee-29d69ac3-2'],
        ['cookie', '__utma=27978091.2013216964.1479228851.1479316541.1479316541.'],
        ['cookie', '__utmb=27978091.1.10.1479316541'],
        ['cookie', '__utmc=27978091'],
        ['cookie', '__utmt=1'],
        ['cookie', '__utmz=27978091.1479316541.1.1.utmcsr=(direct)|utmccn=(direct)|utmcmd=(none)'],
        ['cookie', '_ga=GA1.2.2013216964.1479228851'],
        ['cookie', '_gat=1'],
        ['cookie', 'PHPSESSID=3r9u07ddc62stqf6dph3592pq7']
    ]
    for cookie in cookies:
        request.add_header(cookie[0], cookie[1])

    opener = urllib.request.build_opener(urllib.request.ProxyHandler({'https': '196.145.458.269:8000'}))
    urllib.request.install_opener(opener)
    res = urllib.request.urlopen(request, timeout=600)
    return res.read()

def get_soup(html):
    soup = BeautifulSoup(html)
    return soup

def get_states():
    soup = get_soup(get_html('http://freeemailtrace.com'))
    # тут работа с данными

def main():
    get_states()

if __name__ == '__main__':
    main()

get_states() already works with data. What else can block the site?