set a windows box ( I used W2k professional, not the server).
give the w2k box a static ip address on your internal network.
install the imail demo on it.
install eudora or whatever client you choose on a client box,
or set up accounts on existing clients pointing to this internal address.
set up the accounts you want to test with on the imail server.
test away....
I am using Imail for about 60 users- it works fine on a
PII 450/MHZ 384 MB ram.
good luck!