Microsoft Exchange Server
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Exchange Server 2013 and 2016 logo
|Initial release||April 11, 1993|
|Stable release||2016 RTM (v15.01.0225.042) (October 1, 2015[±])|
|Written in||C++, C#|
|Operating system||Windows Server|
Exchange Server was initially Microsoft's internal mail server. The first version of Exchange Server to be published outside Microsoft was Exchange Server 4.0. Exchange initially used the X.400 directory service but switched to Active Directory later. Versions 4.0 and 5.0 came bundled with an email client called Microsoft Exchange Client. It was discontinued in favor of Microsoft Outlook.
Exchange Server is licensed both in the forms of on-premises software and software as a service. In the on-premises form, customer purchase client access licenses (CALs). In the software as a service form, Microsoft receives a monthly service fee instead (see Microsoft Office 365).
Microsoft had sold a number of simpler email products before, but Exchange Server was an entirely new X.400-based client–server mail system with a single database store that also supported X.500 directory services. The directory used by Exchange Server eventually became Microsoft's Active Directory service, an LDAP-compliant directory service which was integrated into Windows 2000 as the foundation of Windows Server domains.
There have been a number of versions:
- Exchange Server 4.0, March 1996. with five service packs being released over the next two years.
- Exchange Server 5.0
- Exchange Server 5.5
- Exchange Server 2000
- Exchange Server 2003
- Exchange Server 2007, the first to require x64 version of Windows Server.
- Exchange Server 2010, November 9, 2009.
- Exchange Server 2013
Exchange Server 2016
This is the current version, and was released on October 1, 2015 and introduced a number of new features, including:
- Combine Roles: A reduction in the number of available roles to two: a Mailbox Server and an Edge Transport (intended only in certain Office 365 hybrid scenarios).
- Outlook on the web (formerly Outlook Web App): UI changes
- Office 365 hybrid: The Hybrid Configuration Wizard (HCW) that was included with Exchange 2013 is moving to become a cloud-based application. When one chooses to configure a hybrid deployment in Exchange 2016, you'll be prompted to download and install the wizard as a small app.
- Messaging policy and compliance: New DLP and Archiving/Retention/eDiscovery features.
For more detail on new features, see the following Microsoft TechNet article: What's new in Exchange 2016
Clustering and high availability
Exchange Server Enterprise Edition supports clustering of up to 4 nodes when using Windows 2000 Server, and up to 8 nodes with Windows Server 2003. Exchange Server 2003 also introduced active-active clustering, but for two-node clusters only. In this setup, both servers in the cluster are allowed to be active simultaneously. This is opposed to Exchange's more common active-passive mode in which the failover servers in any cluster node cannot be used at all while their corresponding home servers are active. They must wait, inactive, for the home servers in the node to fail. Subsequent performance issues with active-active mode have led Microsoft to recommend that it should no longer be used. In fact, support for active-active mode clustering has been discontinued with Exchange Server 2007.
Exchange's clustering (active-active or active-passive mode) has been criticized because of its requirement for servers in the cluster nodes to share the same data. The clustering in Exchange Server provides redundancy for Exchange Server as an application, but not for Exchange data. In this scenario, the data can be regarded as a single point of failure, despite Microsoft's description of this set-up as a "Shared Nothing" model. This void has however been filled by ISVs and storage manufacturers, through "site resilience" solutions, such as geo-clustering and asynchronous data replication. Exchange Server 2007 introduces new cluster terminology and configurations that address the shortcomings of the previous "shared data model".
Exchange Server 2007 provides built-in support for asynchronous replication modeled on SQL Server's "Log shipping" in CCR (Cluster Continuous Replication) clusters, which are built on MSCS MNS (Microsoft Cluster Service—Majority Node Set) clusters, which do not require shared storage. This type of cluster can be inexpensive and deployed in one, or "stretched" across two data centers for protection against site-wide failures such as natural disasters. The limitation of CCR clusters is the ability to have only two nodes and the third node known as "voter node" or file share witness that prevents "split brain" scenarios, generally hosted as a file share on a Hub Transport Server. The second type of cluster is the traditional clustering that was available in previous versions, and is now being referred to as SCC (Single Copy Cluster). In Exchange Server 2007 deployment of both CCR and SCC clusters has been simplified and improved; the entire cluster install process takes place during Exchange Server installation. LCR or Local Continuous Replication has been referred to as the "poor man's cluster". It is designed to allow for data replication to an alternative drive attached to the same system and is intended to provide protection against local storage failures. It does not protect against the case where the server itself fails.
In November 2007, Microsoft released SP1 for Exchange Server 2007. This service pack includes an additional high-availability feature called SCR (Standby Continuous Replication). Unlike CCR, which requires that both servers belong to a Windows cluster typically residing in the same datacenter, SCR can replicate data to a non-clustered server, located in a separate datacenter.
With Exchange Server 2010, Microsoft introduced the concept of the Database Availability Group (DAG). A DAG contains Mailbox servers that become members of the DAG. Once a Mailbox server is a member of a DAG, the Mailbox Databases on that server can be copied to other members of the DAG. When a Mailbox server is added to a DAG, the Failover Clustering Windows role is installed on the server and all required clustering resources are created.
Like Windows Server products, Exchange Server requires client access licenses, which are different from Windows CALs. Corporate license agreements, such as the Enterprise Agreement, or EA, include Exchange Server CALs. It also comes as part of the Core CAL. Just like Windows Server and other server products from Microsoft, there is the choice to use User CALs or Device CALs. Device CALs are assigned to devices (workstation, laptop or PDA), which may be used by one or more users. User CALs, are assigned to users, allowing them to access Exchange from any device. User and Device CALs have the same price, however, they cannot be used interchangeably.
For service providers looking to host Microsoft Exchange, there is a Service Provider License Agreement (SPLA) available whereby Microsoft receives a monthly service fee instead of traditional CALs. Two types of Exchange CAL are available: Exchange CAL Standard and Exchange CAL Enterprise. The Enterprise CAL is an add-on license to the Standard CAL.
Microsoft Exchange Server uses a proprietary remote procedure call (RPC) protocol called MAPI/RPC, which was designed to be used by Microsoft Outlook. Clients capable of using the proprietary features of Exchange Server include Evolution and Microsoft Outlook. Exchange Web Services (EWS), an alternative to the MAPI protocol, is a documented SOAP-based protocol introduced with Exchange Server 2007, which significantly reduces synchronization time between the server versus WebDAV, which is used by Exchange Server 2003. Exchange Web Services is used by the latest version of Microsoft Entourage for Mac and Microsoft Outlook for Mac. Also, since the release of Mac OS X Snow Leopard, Mac computers running OS X include some support for this technology via Apple's Mail application. Built-in support with Mac OS X 10.6 requires the Exchange organization to be running Exchange Server 2007 SP1/SP2 or Exchange Server 2010.
E-mail hosted on an Exchange Server can also be accessed using SMTP, POP3, and IMAP4 protocols, using clients such as Windows Live Mail, Mozilla Thunderbird, and Lotus Notes. These protocols must be enabled on the server. Exchange Server mailboxes can also be accessed through a web browser, using Outlook Web App (OWA). Exchange Server 2003 also featured a version of OWA for mobile devices, called Outlook Mobile Access (OMA).
Microsoft Exchange Server up to version 5.0 came bundled with Microsoft Exchange Client, a multi-purpose native client for email. After version 5.0, it was superseded by Microsoft Outlook, which was part of Microsoft Office 97 and later. When Outlook 97 was released, Exchange Client 5.0 was still in development and to be later released as part of Exchange Server 5.0, primarily because Outlook was only available for Windows. Later, in Exchange Server 5.5, Exchange Client was removed and Outlook was made the only Exchange client. As part of Exchange Server 5.5, Outlook was released for other platforms.
The original Windows 95 "Inbox" client also used MAPI and was called "Microsoft Exchange". A stripped down version of the Exchange Client that does not have support for Exchange Server was released as Windows Messaging to avoid confusion; it was included with Windows 95, Windows 98, and Windows NT 4. It was discontinued because of the move to email standards such as SMTP, IMAP, and POP3, all of which Outlook Express supports better than Windows Messaging.
Support for Exchange ActiveSync was added to Microsoft Exchange Server 2003. It allows a compliant device such as a Windows Mobile device or smartphone to securely synchronize mail, contacts and other data directly with an Exchange server and has become a popular mobile access standard for businesses due to support from companies like Nokia and Apple Inc. as well as its device security and compliance features.
Exchange ActiveSync Policies allow administrators to control which devices can connect to the organization, remotely deactivate features, and remotely wipe a lost or stolen device. 
Exchange Server hosted as a service
The complexities of managing Exchange Server make it attractive for organisations to purchase it as a hosted service.
This has been possible from a number of providers for more than 10 years, but it is only recently[when?] that many providers have been marketing the service as "cloud computing" or "Software-as-a-Service." Exchange hosting allows for Microsoft Exchange Server to be running in the Internet, also referred to as the Cloud, and managed by a "Hosted Exchange Server provider" instead of building and deploying the system in-house.
Microsoft Exchange Online is an email, calendar, and contacts solution delivered as a cloud service, hosted by Microsoft. It is essentially the same service offered by hosted Exchange providers and it is built on the same technologies as Microsoft Exchange Server. Exchange Online provides end users with a familiar email experience across PCs, the Web and mobile devices, while giving IT administrators or small businesses and professionals web-based tools for managing their online deployment.
Microsoft Exchange is available both as on-premises software and as a hosted service with Exchange Online. Customers can also choose to combine both on-premises and online options in a hybrid deployment.
A hybrid deployment can serve as an intermediate step between an on-premises and a fully hosted Exchange solution. This configuration provides a wealth of features such as allowing organizations to better migrate user mailboxes providing the ability to not only move on-premises mailboxes to Exchange Online, but from Exchange Online back to the on-premises server, cloud-based message archiving for on-premises mailboxes and centralized mailbox management for both infrastructures, to name a few.
With the necessity of on-premises servers; namely an Exchange Server and an Azure Active Directory synchronization server, there is a resource overhead to implement a hybrid solution. Hybrid implementations remain a popular choice for organizations that are unsure of the need or urgency to do a full cut-over to Exchange Online; also allowing for staggered email migration.
Hybrid monitoring and reporting tools cover the main on-premises stack of Microsoft Exchange, Lync, SharePoint, Windows, and Active Directory servers, in addition to using replica data to report cloud user experience. The monitoring of servers is important to the optimal maintenance of the server infrastructure, as well as, cloud reporting to monitor user experience.
Exchange Online was first provided as a hosted service in dedicated customer environments in 2005 to select pilot customers. Microsoft launched a multi-tenant version of Exchange Online as part of the Business Productivity Online Standard Suite in November 2008. In June 2011, as part of the commercial release of Microsoft Office 365, Exchange Online was updated with the capabilities of Exchange Server 2010.
Exchange Server 2010 was developed concurrently as a server product and for the Exchange Online service.
- Comparison of mail servers
- Extensible Storage Engine
- List of applications with iCalendar support
- List of collaborative software
- Innovative Communications Alliance (Microsoft - Nortel)
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