Exim and its periodic calls to internet - A few questions

[Dougie Nisbet <dougie@tbird2.homelan>]

I usually use kmail for my e-mail, but I have exim installed too. I mean to learn about it some day. 
I'm getting some puzzling internet connections that appear to be initiated by exim, but I can't see where it's doing it.
The syslog shows:

>Dec 11 10:23:01 tbird2 /USR/SBIN/CRON[29960]: (mail) CMD (  if [ -x /usr/sbin/exim -a -f /etc/exim/exim.conf ]; then /usr/sbin/exim -q ; fi)
>Dec 11 10:23:01 tbird1 ZyXEL Communications Corp.: board 0 line 0 channel 0, call 230, C01 Outgoing Call dev=2 ch=0 08089933001 .
>Dec 11 10:23:02 tbird1 ZyXEL Communications Corp.: board 0 line 0 channel 0, call 230, C02 OutCall Connected 64000 08089933001 

and this happens every 15 minutes. tbird1 is my ISDN router, and tbird2 is my main server. 
I read the above as saying that user 'mail' has a cron job that runs every 15 minutes which does the following: 

	if [ -x /usr/sbin/exim -a -f /etc/exim/exim.conf ]; then /usr/sbin/exim -q ; fi)

However I can't see any references to exim in any crontables. I've come across this before with syslog (e.g. logrotate); entries 
that appear to be from CRON, but I can't see where they are configured.  Where is it done?

I've commented out the exim entry in /etc/inetd.conf, and deleteted all the S*exim entries in /etc/rc*.d, 
and performed a /etc/init.d/exim stop. All seems ok, but still this entry appears every 15 minutes in syslog! 
I realise that I could probably fix this by removing /etc/exim/exim.conf and the above code snippet will fail, 
but I would rather know a bit more about what is going on behind the scenses.

I have tried to remove exim 'apt-get remove exim' - but the dependencies surprised me. It also removed samba if I remove 
exim, and I want samba. So I need to understand what is causing exim to run every 15 minutes.

This is woody.

Thanks,

Dougie