By default, Postfix multi-instance support logs each instance with its own name (using the syslog_name main.cf parameter).
For example, to find out which instances exist and what their master
PIDs are, use:
# postfix status
This will log information about each instance, with its own name
Changing ps(1) command output is NOT portable. Not all the world
is Linux. In fact there are 10 times as many Macs.
Wietse
