how do i "outsmart" apt-get regarding package dependencies?

["Bryan K. Walton" <thisisnotmyid@tds.net>]

Good Morning,
	We have a new Debian mail server running woody.  I have a question
about this server and apt-get.  There are a number of packages on this
server that we have built from source (apache, sendmail, cyrus) due to
some complex things we include in our builds.
	However, there are a number of programs that I need to install
(logrotate, mailx, etc.) that need an MTA.  apt-get doesn't know or think
that we have one installed since sendmail was compiled from source.
Therefore, it demands to download exim, or another mta of our choice:

-- SNIP --

root@linux2:/home/bryanw# apt-get -f -s install logrotate
Reading Package Lists... Done
Building Dependency Tree... Done
The following extra packages will be installed:
  exim mailx 
The following NEW packages will be installed:
  exim logrotate mailx 
0 packages upgraded, 3 newly installed, 0 to remove and 0  not upgraded.
Inst exim (3.35-1 Debian:3.0r1a/stable)
Inst mailx (1:8.1.2-0.20020411cvs-1 Debian:3.0r1a/stable)
Inst logrotate (3.5.9-8 Debian:3.0r1a/stable)
Conf exim (3.35-1 Debian:3.0r1a/stable)
Conf mailx (1:8.1.2-0.20020411cvs-1 Debian:3.0r1a/stable)
Conf logrotate (3.5.9-8 Debian:3.0r1a/stable)

-- END SNIP --

Is there a way that I can make apt-get realize that we already have an
MTA running?

Thanks,
Bryan Walton