Go here
https://grc.com/x/ne.dll?bh0bkyd2 and click "Proceed". Then click the "Common ports" button. Is 110 open?
All ports are closed by default in ZAP, unless you give a program server permissions or specify firewall-level expert rules. So lets say I misconfigured spampal to accept requests from any user rather than only my PC, and I gave spampal internet server permission in ZAP, then 110 would show as open when scanned from the Internet.
If you've downloaded a piece of software and are using that to scan for open ports, then it will give false results because ports can be open locally but still be inaccessible from the Internet, which is on the other side of your firewall.