If I understand you corectly, that should be easy. The thing to be aware of is it is usually the client that controls whether mail gets deleted, not the server.
An IMAP server may be the best option. With this setup, you can still treat it as a POP3 server if you wish by downloading the mail, but leaving a copy on the server, or you can actually manipulate the mail and create folders from the client without ever downloading it. This way the mail will be organized the same way whichever machine or client you use.
Or you can try Domino server and Lotus Notes. This will probably be as bad Exchange though.
I have a similar setup to allow me to access my mail with any client wherever I am. I use DMAIL from http://netwinsite.com/
was wondering if it was possible to store all mail on the server, the client machines simply browse the mail stored on the server.
IMAP allows that. To the email client, it works just as if the mail and folders were on your local machine. You can add, delete, save drafts etc as normal.
how do I go about getting the server to download mail from an external mail server ready for clients to grab?
Ah... I forgot that little problem
The way I do it is have fetchmail running on my unix box that polls all my different mail accounts and delivers them to the dmail server on my windows machine. Then I just use IMAP from wherever I am to connect the single account on dmail.
Without a unix machine, I'm not sure how to do it. I remember seeing a windows mail server that polled the other accounts for you, but that didn't include an IMAP server. What you need is windows utility like fetchmail. Cygwin might run it, but that's not really the cleanest solution.
I'll have a look around and see if I can find a mail server that includes the polling function.