I've turned on 'Enable cron call on staff's activity' and 'Enable POP3 email fetch' in the settings. Yet, I doubt if a connection with the email server is created. Is there a way to check if it is tried on activity? Emails are still not fetched, and I'm sure the POP3 data is right.
When you save your POP3 information in the Admin Panel, the system should make a connection to your server. If that fails, it will show an error. So your info should be right indeed.
To check whether the cron job is called you can add
echo "CRON CALLED";
exit;
to the file autocron.php. If you then go to the Admin Panel and see this message you know it's called.
If you want to look deeper, try to look at the Cron:(); function. This is where the magic happens :)