I've scrutinised my snapper difference and I seem to have narrowed down the problem to the permissions on /var/lib/dovecot Before path: drwxr-xr-x 1 root root 80 Oct 31 08:06 var/lib/dovecot Post patch: drwxr-x--- 1 root root 80 Oct 31 12:46 var/lib/dovecot Switching the permissions back seemed to have moped up all the problems.