You can suggest him to install Scalix, its a mail server app, for linux as well it gives the look and feel as of windows. So if you IT manager is strong hand in dealing with gui he/she can also able to handle this very efficiently, as well this server provides the connectivity for the mobile users. Scalix is based on HPOpenMail engine that incorporates groupware features for Web, Outlook, and Novell Evolution clients.
When it comes to security, anti-spam, anti-virus, archiving, and other functionality, Scalix takes an unusual approach — "via 3rd party interface." Most other comparable servers, whether on Linux or Windows, support (and often include) specific third-party products in their package. For anti-virus, Scalix lists Clam AV, McAfee, and Trend Micro InterScan VirusWall as compatible. For anti-spam, only Spam Assassin is listed. This approach is nothing if not open-ended; you are free to choose. However, the acquisition, installation, and configuration of these products is not an altogether simple process. If there are difficulties, to which party do you turn? Other products, for example the Merak Linux Mail Server, not only ship with integrated third-party anti-virus and anti-spam functions but also provide related security enhancements of their own.
Which seems difficult with the Microsoft, I think it will help you to convey to IT manager and you can find more about Scalix on web links also.
YM! - call_2_adarsh