Eventlet SMTP relay server

# import the standard smtplib libraryimport smtplibfrom eventlet import patcherpatcher.monkey_patch(all=False, socket=True) # patch socket and sslimport eventletimport sysimport emailimport getoptdef local_property(func):    return property(**func())class SMTPRelayServer(object):    def __init__(self, host=None, port=None, ssl=False, listen_addr=('0.0.0.0', 6000)):        """host is the ip address of the server, can be optional        port is the port of the server, can be optional        if ssl is required to connect to the server, it must be True        listen_addr is a tuple of current server address        """        self.address = listen_addr        self.host = host        self.host_port = port        self.require_ssl = ssl        self.pool = eventlet.GreenPool()        self.send_addr = 'smtp_relay'    @local_property    def send_from():        def fget(self):            return self.send_addr        def fset(self, v):            self.send_addr = v        return locals()    @local_property    def username():        def fget(self):            return self.user        def fset(self, v):            self.user = v        return locals()    @local_property    def passwd():        def fget(self):            return self.pwd        def fset(self, v):            self.pwd = v        return locals()    def run(self):        """main loop of the relay server"""        self.server_sock = eventlet.listen(self.address)        while True:            new_sock, address = self.server_sock.accept()            print 'incomming: ', address            self.pool.spawn_n(self._handle, new_sock.makefile('r'))    def shutdown(self):        """shtudown the server"""        self.server_sock.close()    def _handle(self, sock):        """client handler, forward the client data to the remote smtp server"""        content = ''        while True:            data = sock.read()            if not data: break            content += data        # client data is mail message, extract the From and To addresses        msg = email.message_from_string(content)        if msg['From']:            from_addr = msg['From']        else:            from_addr = self.send_addr        # only send the mail if To is not empty        if msg['To']:            if not self.require_ssl:                smtp_server = smtplib.SMTP(self.host, self.host_port)            else:                smtp_server = smtplib.SMTP_SSL()                smtp_server.connect(self.host, self.host_port)                smtp_server.login(self.username, self.passwd)            smtp_server.sendmail(from_addr, msg['To'], content)    # context manager protocal    def __enter__(self):        return self    def __exit__(self, exec_type, exec_value, traceback):        self.shutdown()        return Falseif __name__ == '__main__':    host = None    port = None    user = ''    pwd  = ''    ssl = False    opts, args = getopt.getopt(sys.argv[1:], "", ['host=', 'port=', 'user=', 'pwd=', 'ssl'])    for opt, arg in opts:        if opt == '--host':            host = arg        elif opt == '--port':            port = arg        elif opt == '--user':            user = arg        elif opt == '--pwd':            pwd = arg        elif opt == '--ssl':            ssl = True    with SMTPRelayServer(host, port, ssl) as server:        server.username = user        server.passwd = pwd        server.run()