I don't know exactly how to ask what I'm looking fore so I'll just explain it.
I would like to do something at my work so that people could read their mail and set calender appointments internally. Something like MS Exchange but since there isn't an exchange server around would like to use something opensource.
I was looking at eGroupWare but emails I don't have access to the email server since the service is being hosted outside.
So does anyone know of a software that would allow outside emails and calender and tasks and address book so that they are connected. I mean it can be an application but it has to run also on windows or it can be a web application.

I'll really appreciate any advice here.

Thanks for the help.