Memory staying in cached status -- Possible Memory Leak

[Kaplan, Andrew H.]

Hi there --

I am running Fedora Core 5 that was hardened by Bastille Linux on a system with
1.5 GB of RAM. The system functions as an e-mail server running Sendmail along
with MailScanner, SpamAssassin, and ClamAV. 

I have noticed over time, via the free -m command, that the amount of cached RAM
is going up. This results in the amount of free memory going down to where there
is almost nothing left. The end result has been the system to periodically
hanging, which forces me to reboot the server. 

What can I do to correct this problem? Thanks.