Cost of a mail server

Hardware, bandwidth, processing : how does it behave?

[goldminer]

In the WebmasterWorld community building forum we ve been discussing about projects to launch community oriented freemail services. [webmasterworld.com]

Now we need to know how much it can cost.
Is it server/bandwidth intensive? And even more important, how does it behave with time?
Are the costs exponentially increasing?

Let s start on a 50 suscribers/day basis, on a site that hits 4 millions pages/month. Any ideas? Experience reports? That would be great! Thanks.