Internet e-mail protection prevents Outlook from connecting to mailserver

Hi.

During the summer, my customer has started having issues receiving mail. 
 

There was no connections to the mailserver outgoing from the PC (according our firewalllogging), so
I disabled SEP completely on the PC - and it worked. Then I went in and tested disabling one or two modules at a time, 
untill I found the culprit. It wasn't the outlook protection, but internet e-mail protection plugin.

This PC runs a unmanaged SEP client and recieves it's updates directly from Symantec, and it was updated yesterday.
It's been running the client since 2011 without issues. So something new must have happened during the summer.

Any suggestions to how to fix this?