Postfix can attach a call tracer whenever a daemon process
starts. Call tracers come in several kinds.
System call tracers such as trace, truss,
strace, or ktrace. These show the communication
between the process and the kernel.
Library call tracers such as sotruss and ltrace.
These show calls of library routines, and give a better idea of
what is going on within the process.
Append a -D option to the suspect command in
/etc/postfix/master.cf, for example:
smtp inet n - n - - smtpd -D
debugger_command definition in /etc/postfix/main.cf
so that it invokes the call tracer of your choice, for example:
(truss -p $
process_id 2>&1 | logger -p mail.info) & sleep 5
Type "postfix reload" and watch the logfile.