At least in Debian-based distros (like Ubuntu), changes for service foo should go into /etc/default/foo, not directly to /etc/init.d/foo. In this case, the PIDFILE="/var/spool/postfix/var/run/${NAME}/saslauthd.pid" option should go to /etc/default/saslauthd, where it will override the PIDFILE setting from /etc/init.d/saslauthd. Background: /etc/default/saslauthd is a "conffile"; changes in it won't be touched by updates. /etc/init.d/saslauthd is not a conffile and may be overwritten by the next update.