logging of pop sessions in syslog (qpopper 2.52)

[PM WONG]

We have qpopper 2.52 running on both aix and digital unix
On both machines,  there's the line 
mail.debug     /var/spool/mqueue/syslog

However, only the logging of pop connections appear in
that of digital unix but not on aix
I should presume the syslog were enabled by default during 
the 'make ' process of qpopper 2.52
Why didn't it get logged in aix ?
If i am to recomplie it again on aix, which option should
i enable explicitly so as to ensure the logging to syslog
will be achieved.