Ubuntu (past/present) has a broken Postgrey SysV /etc/init.d (start(up)/status/stop) file - and possibly will not startup (default install) on a reboot/etc. This will have an ill effect on mail delivery (postfix/etc).
Here is one that works. Make sure you either replace entire file with one below or edit the pertinent lines.
Remember that this is not an upstart override - you are editing a SysV init file directly.