There are load of programs around that do what you want.
You can either have them just notify you when you have new mail (without downloading the main from your mail-server for you) or you can have a fully functional email client that will let you browse/reply/delete messages etc.
For a huge collection try CNET Download.com and search for EMAIL.
All these programs will run independantly of Outlook and should be fully compatible.
Hope this helps!