Ubuntu :: Evolution Receives Mails Only Once

I created three pop accounts in evolution. For jka-walgau.at my name, office and mobile. The first time everything ran ok (all new mails could be downloaded, and from each account mails could be send). After a day (iIset the computer up for a friend) there arent no new mails that come in (webinterface tells me there are new ones).
SSL for pop and TLS for smtp were set.
The problem is they are selfsigned certificates. The first time when I configured the accounts and clicked the button to test the authentication methods I got a warning (self signed) no button to add this cert permanently only a OK buttton and in the upper corner the (x) to close. How should I handle this problem.