sasl2 gentoo not working

[delay_2010]

OK, I got it myself.
It did not look like a chrooted postfix in my install. But this is the case: postfix is chrooted.
I looked via /proc file system which file the postfix/smtpd process saw and correct: it could not see /etc/sasl2/sasl2db.
I now symbolic linked the file /etc/sasl2/sasl2db with /var/spool/postfix/etc/sasl2/sasl2db and used incrond to change owner- and accessrights for this file if it gets changed via ispcp.
Now it works.