Which ports are used on a ISPConfig 3 server and shall be open in the firewall?

Here is a list of ports that are used commonly on ISPConfig 3 servers. If you don't have all services installed or if you e.g. don't want to connect to MySQL from external servers, then close the unused or unwanted ports.

TCP ports

20 - FTP Data
21 - FTP Command
22 - SSH
25 - Email
53 - DNS
80 - HTTP (Webserver)
110 - POP3 (Email)
143 -Imap (Email)
443 - HTTPS (Secure web server)
993 - IMAPS (Secure Imap)
995 - POP3S (Secure POP3)
3306 - MySQL Database server
8080 - ISPConfig web interface
8081- ISPConfig apps vhost

UDP ports

53 - DNS
3306 - MySQL