But at the end of the day, an email system needs to be secure, and not just secure but able to maintain absolute security when your system is being updated.

This is why I think that Zimbra, is an open source product that has been designed with future safety in mind.

Zimbra's Collaboration Suite has been designed with several levels of security for both end users (virus, spam, phishing protection) and to the overall ZCS architecture / deployment framework (authentication, encryption).

The ZCS server comes embedded with ClamAV, the award-winning open source AV system

To support highly secure deployments Zimbra Collaboration Suite is designed with a classic network security model where server-side systems must be trusted, but the client-side need not be. Thus, with the server physically protected businesses and organizations can deliver secure messaging and collaboration to their end users anywhere, even on their home computers, public Internet kiosks, etc. (without being forced to deploy costly Virtual Private Networks).

Other Web Client Security Benefits

The ZCS web client is an Ajax-based application, which offers many advantages over traditional products:

    * Web client is downloaded - Ajax client code is downloaded on demand from the trusted ZCS server after a particular user logs-in. No software is left on the client for a malicious person to tamper with.

    * No persistent caching of user data - A substantial exposure with traditional web mail clients is that they cache HTML data including message contents, and addresses. By avoiding caching user data on disk, this security vulnerability is avoided.

• Server-side control of Zimlet mash-ups - Zimlets and other mash-ups are prevented from accessing arbitrary services on the Internet. This means the ZCS server can act as a secure, proxy gateway for accessing intranet applications, and can govern which web services are accessible for mash-up within the Zimbra Ajax web clients.

But the bottom line is overall network security open source is a more secure solution than Windows.