Gartner: MarketScope for E-Mail Systems

The past year brought substantial progress in the long march toward provision of e-mail as a cloud service, but most activity still centers on premises-based offerings. Against this background, Gartner evaluates eight providers of e-mail systems.

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Long story:

http://www.gartner.com/technology/media-products/reprints/microsoft/vol10/article19b/article19b.html