ECM is specifically for OS X Server 10.3+. (Panther). If you had an earlier installation from my site for Jaguar, you will have to do a complete reinstall of ECM. Even the uid's and gid's for the various packages have been changed.

After installing all the packages, you will have to follow all steps of the installation procedure in order to make this mail-system functional.

I have not tested on "plain" 10.3+ Panther client, so you should do that at your own risk. Actually, do everything at your own risk!