in Planet Debian ~ read.

Making SASL2 working with postfix in sarge

Stop SASLAUTHD service

Create directory for runtime files

# mkdir -p /var/spool/postfix/var/run

Move sockets into chroot

# mv /var/run/saslauthd /var/spool/postfix/var/run/

Create symlinks, so that the old setup with the default locations is still intact

# ln -s /var/spool/postfix/var/run/saslauthd /var/run

Make sure the postfix user (postconf mail_owner) has access to the directory /var/spool/postfix/var/run/saslauthd
For me, I needed to add the user postfix to the group mail.

Restart SASLAUTHD