- Google Apps - The search giant’s cloud productivity suite probably bears no introduction, but a relentless anti-Microsoft PR campaign coupled with the drive to make it easier for administrators to migrate from Exchange makes it probably the biggest threat to Redmond’s supremacy - as evidenced by the fact that Microsoft singles them out for counter-marketing moves.
- Zoho - Where Google Apps goes after both the consumer and enterprise spaces, Zoho is constantly releasing new enterprise-focused SaaS applications like Zoho Invoice and Zoho Helpdesk. But it doesn’t stop them from finding new users by integrating with Google.
- HyperOffice - Like Zoho, HyperOffice is looking for enterprise users. Sold and packaged as a full-fledged replacement for Microsoft Exchange and SharePoint, users get a lot of functionality (and a graphical inferface) typically associated with desktop environments, all in the browser. It even pushes to your iPhone.
- IBM LotusLive - While the Microsoft/IBM rivalry isn’t quite back up to the levels of old, Big Blue’s cloud version of Lotus Notes is still a force in the channel.
- VMware - The most recent entry to this list is also the most mysterious. The launch of the Zimbra open-source email appliance marks the real start of their push against Microsoft Exchange. But VMware is a powerful enough player in the market to make them worth watching.
- Open-Xchange, which has significant momentum with VARs and MSPs that are moving into SaaS-centric email solutions.
- There is no number seven. The VAR Guy doesn’t play by the rules and neither do I.
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