I have a Windows 2012 R2 server used as web server, with ports for web (80, 443, and 8080) open for public sites hosted on it. Doing some security checks on it, I found it's listening on port 110 too:
However, there is no POP3 service, or any mail service, running on that server.
It has both node.js and IIS installed, in case it's relevant.
The weird part is that port 110 is not listed when running
netstat -na on the server, and it can't find anything listening on that port:
I even added inbound/outbound rules to block port 110 on the server in the Firewall. Still no effect.
I can even connect with telnet to that port and send data, though the display is weird:
Why and how is this port open? How to block it?