There are four rankings. According to the 20 1 1 China self-built enterprise mailbox market share data calculated by iResearch, Microsoft's Exchange ranks first with the market share of 18. 1%; IBM's Lotus Domino/Notes ranked second with 6.0%, while Shi Ying's Coremail and Zhong Yi Post's eYou ranked third and fourth with 4.2% and 1.5% respectively.
If you choose domestic products, you'd better choose Coremail.