Plesk requires different open ports depending on the type of services you need on your server. For example, for FTP transfers, it is necessary to open ports #20 and #21; for web hosting services, you must open port #80; if what you want are POP3 and SMTP email services, you need to open ports #25 and #110. You need to know which services you want to use in order to determine which ports you need to open.
Ports that Plesk has by default
#20 –>ftp-data
#21 –>ftp
#22 –>ssh
#25 –>smtp
#53 –>dns (TCP and UDP)
#80 –>http (Web Server (e.g., Apache) and Plesk updater)
#106 –>poppassd (Localhost only)
#110 –>pop3
#113 –>auth
#143 –>imap
#443 –>https
#465 –>smtps
#587 –>mail submission
#990 –>ftps
#993 –>imaps
#995 –>pop3s
#3306 –>mysql
#5224 –>(External connections only) Plesk license update
#5432 –>postgres
#8443 –>plesk-https
#8880 –>plesk-http
#9080 –>tomcat
Note
All our clouding.io servers with the pre-installed Plesk control panel already have the necessary ports open, so no additional action is required for their proper operation. The ports you should leave open in your firewall will depend on the services running on your server, as mentioned above.