I am using an ISPConfig 3.2.12. Recently, I have found a new TCP port 4190 which is listening on all addresses. 0.0.0.0:4190 :::4190 What is this and should I open it in my firewall?
That's the port of sieve. Sieve is part of Dovecot typically packaged as -pigeonhole. One can setup server-side filter rules for incoming mails. You can compare it with rules in MS Exchange.
