On Debian Sid i have seen that ufw service is stopped on logrotate!! Its a bad known bug! Workaround: Set all Services like Dovecot, Postfix to listen on LOCALHOST (127.0.0.1) if not needed over Internet Enable ONLY encrypted AUTH (Login) to Postfix! (TLS 1.2) Disable unneeded Services ! like Samba, FTP… move config from /etc/logrotate.d/ufw to /root/ to disable ufw logrotate !! edit /etc/ufw/ufw.conf set LOGLEVEL to “off” restart the Server and check open Ports next Days from outside with: $sudo nmap -PN my.server.com