Second, it gives VMware a way to reach small- and mid-sized companies that often avoid VMware even when they are interested in virtualization because its price tag is higher than that of Microsoft or Citrix for similar configurations.
Zimbra also offers a good killer app for desktop virtualization – a market for which VMware has a host of good products but not a lot of market momentum.
VMware boosted Zimbra's appeal by adding support for its Project Horizon APIs for non-PC devices and third-party software.
VMware also reconfigured Zimbra so it can be installed and used in nearly as many ways as Citrix' virtual desktop clients. You can install it as an internal cloud service, use it primarily on mobile devices, as an appliance, have it hosted externally by a cloud service provider, use the open-source version rather than proprietary, or use actual desktop software rather than just a web browser so you can tell where your mail and documents actually are.
When Yahoo owned Zimbra during 2007 and 2008 it converted the suite to de-emphasize client software in favor of a web front end to Yahoo's mail service, to which the client returned compulsively if it didn't have a local Zimbra server to serve as a home base.
In the year since VMware bought it, Zimbra's user base has expanded to 66 million mailboxes. That's a lot of weight to throw on VMware's virtualization and cloud efforts in the SMB market. Maybe not enough to counter Citrix' lead there, but still a lot.
That's an issue for virtualization vendors, though. The most important thing for end users is that VMware is using a low-cost, high-function set of applications as the lead attraction for its platform products, which are normally invisible to end users, and properly so.
Citrix did that to a certain extent by making it easier to use an iPhone, iPad or other device as front end to a secure virtualized work identity. Even using it, end users don't recognize what it is, or why Citrix should be important to them.
As a vendor, if you can put an email client in the hands of end users and get them to love it, you've bypassed IT and landed yourself a permanent contract. I haven't played with version 7 yet, so I can't say whether it's better than the almost-good-enough-to-dump-Outlook client it used to be.
But it's still a smart strategy for VMware.