digged the web and nearly drove crazy. By entering
ls -la /var/spool/postfix/var/run/saslauthd
it had shown, that the directory is empty.
After literally hours of search i came across this. Stop the instance of saslauthd and restart it.
/etc/init.d/saslauthd stop-instance saslauthd /etc/init.d/saslauthd start-instance saslauthd
this fixed it.
Just in case.