I tried to connect to your server with telnet:
telnet smtp.ermedia.nl 25
Connected to smtp.ermedia.nl.
Escape character is '^]'.
220 duduk.ermedia.nl ESMTP Postfix
250-AUTH PLAIN LOGIN
Connection closed by foreign host.
It's working, but it took some time (~30 seconds) until I got connected... Might be a firewall problem, might be a problem with your setup, though I can't see anything wrong in what you posted...
Nov 11 14:06:55 duduk ipop3d: Mailbox vulnerable - directory /var/spool/mail must have 1777 protection
chmod 1777 /var/spool/mail