网友说法：
Exchange服务器版其实价格不高，企业版也就是几万左右，贵的是客户端授权，一个客户端授权大概要300多。但是，但是，中国企业买Exchange客户端一般都是可以按比例买的，比如10%-20%。一般你买到这个比例，微软基本就睁一只眼闭一只眼了。我们公司就是微软金代，很多项目上都是这个操作的，呵呵。
论坛资料
Exchange Server 2010 on-premises is licensed in the Server / Client Access License (CAL) model in exactly the same way that Exchange Server 2007 was licensed. There are three types of licenses:
1. Server Licenses
A license must be assigned for each instance of the server software that is being run. The Exchange Server license is sold in two server editions:
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Standard Edition: designed for the mailbox needs of small to medium organizations. Also appropriate for non-mailbox roles in a larger Exchange deployment.
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Enterprise Edition: designed for larger organizations that may require a greater number of mailbox databases.
2. Client Access Licenses (CALs)
Exchange requires a CAL for each user or device that accesses the server software. There are two types of CALs for Exchange:
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Standard CAL: designed to help users be more productive from virtually any platform, browser, or mobile device, with new features in Exchange Server 2010 that help manage communications overload and lower helpdesk costs.
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Enterprise CAL: designed to allow organizations to reduce the costs and complexity of meeting compliance requirements with new integrated archiving functionality and information protection capabilities, while also helping you cut costs by replacing legacy voice mail systems with Unified Messaging.
The Enterprise CAL is sold as an add-on to the Standard CAL. To enable Standard CAL features for a user, the user must be licensed with just the Standard CAL. To enable Enterprise CAL features, the user must be licensed with one Standard CAL plus one Enterprise CAL.
Note: Both CALs work with either Server Edition.
3. External Connector Licenses
An External Connector permits an unlimited number of clients to access an Exchange Server in scenarios where the number of CALs is uncertain.
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Access via the External Connector is limited to non-employees such as partners, suppliers, customers, and retirees.
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The number of External Connector licenses required corresponds to the number of servers in the organization’s Exchange environment.
