"With VMware buying Zimbra I feel much more confident," said Cedric Halbach, CTO at , which has used Zimbra successfully for companywide e-mail for about four years. "The Zimbra software is great, but it was in the wrong place in Yahoo's hands and that made its future insecure for me."

Prior to implementing Zimbra, The Metropolitan Companies used Exchange, but ditched it after finding it too expensive and unstable. Thus, Microsoft's attempt to buy Yahoo, and the search deal the vendors later struck, concerned Halbach.

"We absolutely weren't going back to Exchange. We’ve used it in the past and had too many problems with it, and it is very expensive once you get into the larger rollouts," he said in a phone interview.

"Even now with Microsoft as a Yahoo partner, there’s still a gray haze in the background that I’ve been aware of and keeping my eye on, kind of on a wait-and-see [mode] while still using Zimbra, which is excellent, very powerful and reliable," Halbach said.

Zimbra has worked so well at the company for its about 200 users that Halbach and partners, including the owner of The Metropolitan Companies, recently launched a startup venture called to provide the Zimbra suite and other software and services on a hosted basis for small businesses.