def receive_thread(number):
srv = POP3(host=self.url, timeout=5)
srv.user(email_name)
srv.pass_(email_pwd)
rsp, lines, octets = srv.retr(number）
msg_byte = b'\r\n'.join(lines)
msg_content = msg_byte.decode(chardet.detect(msg_byte)['encoding'])
msg = Parser().parsestr(msg_content)

def email_download():
with ThreadPoolExecutor(max_workers=6) as pool:
numbers =200
futures = [pool.submit(receive_thread, i) for i in range(numbers, 0, -1)]
for future in futures:
print(future.result())

t1 = threading.Thread(target=email_download)
t1.start()

只要带有网络请求的就会被阻塞，导致线池的线程被阻塞了，程序退出了，线程没有退出求解决方案，谢谢！