Python3 requests 通过代理抓取数据出错

Question

我准备通过代理来爬取信息，测试代理是类似下面的

for p in proxies:
    print(p)
    s = requests.session()
    url = "https://mail.163.com/"
    s.keep_alive = False
    s.proxies = {"https": p}
    s.headers = {
                    "User-Agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:74.0) Gecko/20100101 Firefox/74.0",
                    "Connection": "close",
                }
    r = s.get(url)
    print(r.status_code)

不过出现了错误提示

ProxyError: HTTPSConnectionPool(host='mail.163.com', port=443): Max retries exceeded with url: / (Caused by ProxyError('Cannot connect to proxy.', NewConnectionError('<urllib3.connection.VerifiedHTTPSConnection object at 0x7fdacdb5d518>: Failed to establish a new connection: [Errno 11] Resource temporarily unavailable',)))

不使用代理是正常的。想问问大伙，上面的代码还缺少什么呢？