Another selling point is that the Zimbra client works across a wide range of devices, including BlackBerry, iPhone, and Android, with synchronization maintained across multiple clients. You can also use Outlook as a client if you prefer.
According to VMware, Zimbra already has over 55 million mailboxes in operation (much of those maintained by service providers or deployed in the education market). It's a little odd thinking of VMware as an application company, but with VMware sales and support backing Zimbra, I think this challenge to Exchange has some real possibilities.
This article, "Can VMware put a dent in Microsoft Exchange?" originally appeared at InfoWorld.com. Read more of Eric Knorr's Modernizing IT blog and get a digest of the key stories each day in the InfoWorld Daily newsletter and on your mobile device at infoworldmobile.com.