Scratched Out

I run a small company and am trying like crazy to get rid of all the windows systems. Currently I use an application called MDaemon for email. While I dislike that it's windows only, it is painfully easy to do everything you need. Having run it on both windows98 and windowsxp I can tell you it's rock solid. Not often I would recommend a windows app.. but there it is. It also supports dial up so you can grab all your email via dial-up earthlink and then parse them locally if you like.

On the client side- I'd go with gnu/linux. Keep it simple with a KDE interface and an easy to install distro (Mandrake). Kmail is one of the better mail apps out there and mozilla and openoffice should complete your must-have desktop applications.

There's also a really great set of articles written by Colin Mattoon of Linuxworld on setting up a small business with linux. Link's not handy but I'm sure you can google for it.

IMAP doesn't store it's mails on the webserver, IMAP4 is just a protocol like POP3, so
it doesn't really matter what you choose.
The only real difference is that the IMAP4 protocol allows email messages to be manipulated (like categorized into folders) on the email server.
Use POP3 and download all your mails at once.
I'm guessing you work with redhat, and the default RH pop3 server has SSL support.
Just configure your smtp server to run a different port.
Say what distro you're using and I'm sure someone will tell you