is SMTP blocked or filtered?
Set up postfix on a droplet but trying to connect remotely to port 25 there is no response, although the connection is not rejected or closed. There is no response via nc or telnet on that port. ufw is set up to allow it with a rule ACCEPT tcp -- anywhere anywhere tcp dpt:smtp And on the droplet, 'nc localhost smtp' works as expected. Is DO filtering or blocking port 25 upstream?