Microsoft Exchange Server is the server side of a client–server, collaborative application product developed by Microsoft. It is part of the Microsoft Servers line of server products and is used by enterprises using Microsoft infrastructure products. Exchange’s major features consist of electronic mail, calendaring, contacts and tasks; support for mobile and web-based access to information; and support for data storage.
Planning the migration from Microsoft’s internal “legacy XENIX-based messaging system” to the Exchange Server environment began in April 1993, and by January 1995 some 500 users were running on Exchange Server Beta 1. By April 1996 32,000 users were migrated to that environment.
Windows Messaging, initially called Microsoft Exchange, is an e-mail client that was included with Windows 95 (beginning with OSR2), 98 and Windows NT 4.0. In Windows 98, it is not installed by default, but available as a separate program in the setup CD. Microsoft Exchange gained wider usage with the release of Windows 95, as this was the only e-mail client that came bundled with it. Exchange was included throughout later releases of Windows up until the initial release of Windows 98, which by then also included Outlook Express 4.0.
- In 1996, Microsoft Exchange was renamed to Windows Messaging, because of Microsoft’s release of another Exchange product, which was meant for servers.
- Windows Messaging had two branches of successors:
Microsoft Fax, also called Microsoft at Work Fax (AWF), is the fax component to provide Send-and-Receive Fax capability; sent and received faxes were stored in the same .pst file as other messages, first attempt of unified messaging by Microsoft; also the ability to act as fax server, which was not available in later versions of Windows until Windows Vista.
- Because Microsoft Outlook used the same basic Windows Messaging profile, account and e-mail settings (MAPI), Microsoft Exchange users not familiar with it could have been led into thinking that Outlook created a double profile and that it made copies of all their mail while they were just checking to see what the new Microsoft Outlook (ver. 97) looked like. This way some MS Exchange users could have unknowingly deleted all their e-mail that they perceived to be ‘double’, as Microsoft Outlook did not have any front-end feature to notify users that it was actually using the same MS Exchange / Windows Messaging account.
- The original version lacks support of Internet mail (SMTP and POP3 support). They are only available with the separate Microsoft Plus! pack.
- No support for International characters. Some e-mail that was sent with a non-ASCII or non-7/8-bit character set, was shown in the form of text attachments, which had to be saved and then read in a web browser, with the browser’s text encoding set for a specified code page.
- HTML e-mail was shown in such a way that the message contained an *.ATT or *.htm attachment, which had to be saved and then viewed in a browser, as MS Exchange did not have support for HTML-formatted messages.
- In a similar fashion, e-mail that did not use traditional message formatting, was shown the same way: actual message content was delivered in the form of text attachments with the *.ATT extension, which could be opened through Notepad. These files were in turn saved in the active Temp directory and some sensitive e-mail could therefore have been made available for other users to see.
 Exchange Server 4.0
Exchange Server 4.0, released on June 11, 1996, was the original version of Exchange Server sold to the public, positioned as an upgrade to Microsoft Mail 3.5. The original version of Microsoft Mail (written by Microsoft) had been replaced, several weeks after Lotus acquired cc:Mail, by a package called Network Courier, acquired during the purchase of Consumer Software Inc. in April 1991. Exchange Server was however 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 server. Active Directory was integrated into Windows 2000 as the foundation of Windows Server domains.
 Exchange Server 5.0
On May 23, 1997, Exchange Server 5.0 was released, which introduced the new Exchange Administrator console, as well as opening up “integrated” access to SMTP-based networks for the first time. Unlike Microsoft Mail (which required a standalone SMTP relay), Exchange Server 5.0 could, with the help of an add-in called the Internet Mail Connector, communicate directly with servers using (reference missing) . Version 5.0 also introduced a new Web-based e-mail interface Exchange Web Access, this was rebranded as Outlook Web Access in a later Service pack. Along with Exchange Server version 5.0, Microsoft released version 8.01 of Microsoft Outlook, version 5.0 of the Microsoft Exchange Client and version 7.5 of Microsoft Schedule+ to support the new features in the new version of Exchange Server.
Exchange Server 5.5, introduced November, 1997, was sold in two editions, Standard and Enterprise. They differ in database store size, mail transport connectors and clustering capabilities. The Standard Edition had the same 16 GB database size limitation as earlier versions of Exchange Server, while the Enterprise Edition had an increased limit of 16 TB (although Microsoft’s best practices documentation recommends that the message store not exceed 100 GB). The Standard Edition includes the Site Connector, MS Mail Connector, Internet Mail Service (previously “Internet Mail Connector”), and Internet News Service (previously “Internet News Connector”), as well as software to interoperate with cc:Mail, Lotus Notes and Novell GroupWise. The Enterprise Edition adds an X.400 connector, and interoperability software with SNADS and PROFS. The Enterprise Edition also introduced two node clustering capability. Exchange Server 5.5 introduced a number of other new features including a new version of Outlook Web Access with Calendar support, support for IMAP4 and LDAP v3 clients and the Deleted Item Recovery feature. Exchange Server 5.5 was the last version of Exchange Server to have separate directory, SMTP and NNTP services. There was no new version of Exchange Client and Schedule+ for version 5.5, instead version 8.03 of Microsoft Outlook was released to support the new features of Exchange Server 5.5.
 Exchange 2000 Server
Exchange 2000 Server (v6.0, code name Platinum), released on November 29, 2000, overcame many of the limitations of its predecessors. For example, it raised the maximum sizes of databases and increased the number of servers in a cluster from two to four. However, many customers were deterred from upgrading by the requirement for a full Microsoft Active Directory infrastructure to be in place, as unlike Exchange Server 5.5, Exchange 2000 Server had no built-in Directory Service, and had a dependency upon Active Directory. The migration process from Exchange Server 5.5 did not have any in-place upgrade path, and necessitated having the two systems online at the same time, with user-to-mailbox mapping and a temporary translation process between the two directories. Exchange 2000 Server also added support for instant messaging, capability was later spun off to Microsoft Office Live Communications Server.
 Exchange Server 2003
Exchange Server 2003 (v6.5, code name Titanium) debuted on September 28, 2003. Exchange Server 2003 (currently at Service Pack 2) can be run on Windows 2000 Server (only if Service Pack 4 is first installed) and 32-bit Windows Server 2003, although some new features only work with the latter. Like Windows Server 2003, Exchange Server 2003 has many compatibility modes to allow users to slowly migrate to the new system. This is useful in large companies with distributed Exchange Server environments who cannot afford the downtime and expense that comes with a complete migration.
The June 2, 2003, release of Exchange Server 2003 made the migration from pre-2000 versions of Exchange significantly easier (although still involved the same basic steps), and many users of Exchange Server 5.5 waited for the release of Exchange Server 2003 to upgrade. The upgrade process also required upgrading a company’s servers to Windows 2000. Some customers opted to stay on a combination of Exchange Server 5.5 and Windows NT 4.0, both of which are no longer supported by Microsoft.
One of the new features in Exchange Server 2003 is enhanced disaster recovery which allows administrators to bring the server online more quickly. This is done by allowing the server to send and receive mail while the message stores are being recovered from backup. Some features previously available in the Microsoft Mobile Information Server 2001/2002 products have been added to the core Exchange Server product, like Outlook Mobile Access and server-side Exchange ActiveSync, while the Mobile Information Server product itself has been dropped. Better anti-virus and anti-spam protection have also been added, both by providing built-in APIs that facilitate filtering software and built-in support for the basic methods of originating IP address, SPF (“Sender ID”), and DNSBL filtering which were standard on other open source and *nix-based mail servers. Also new is the ability to drop inbound e-mail before being fully processed, thus preventing delays in the message routing system. There are also improved message and mailbox management tools, which allow administrators to execute common chores more quickly. Others, such as Instant Messaging and Exchange Conferencing Server have been extracted completely in order to form separate products. Microsoft now appears to be positioning a combination of Microsoft Office, Microsoft Office Live Communications Server, Live Meeting and Sharepoint as its collaboration software of choice. Exchange Server is now to be simply e-mail and calendaring.
Exchange Server 2003 added several basic filtering methods to Exchange Server. They are not sophisticated enough to eliminate spam, but they can protect against DoS and mailbox flooding attacks. Exchange Server 2000 supported the ability to block a sender’s address, or e-mail domain by adding ‘*@domain.com’, which is still supported in Exchange Server 2003. Added filtering methods in Exchange Server 2003 are:
- Connection filtering
- Messages are blocked from DNS RBL lists or from manually specified IP addresses/ranges
- Recipient filtering
- Messages blocked when sent to manually specified recipients on the server (for intranet-only addresses) or to any recipients not on the server (stopping spammers from guessing addresses)
- Sender ID filtering
- Sender ID, a form of Sender Policy Framework (SPF)
- Intelligent Message Filter
- A free Microsoft add-on that uses heuristic message analysis to block messages or direct them to the “Junk E-Mail” folder in Microsoft Outlook clients.
Exchange 2003 mainstream support ended on April 14, 2009.
Exchange Server 2003 is available in two versions, Standard Edition and Enterprise Edition. Standard Edition supports up to two storage groups (with one of the storage groups, called the recovery storage group, being reserved for database recovery operations) and a maximum of 2 databases per storage group. Each database is limited to a maximum size of 16GB. Beginning with the release of Service Pack 2, Standard Edition allows a maximum database size of 75 GB, but only supports 18 GB by default; larger sized databases have to be updated-in with a registry change. Enterprise Edition allows a 16 TB maximum database size, and supports up to 4 storage groups with 5 databases per storage group for a total of 20 databases per server.
Exchange Server 2003 is included with both Microsoft Small Business Server 2003 Standard and Premium editions and is 32-bit only, and will not install on the various 64-bit versions of Windows Server 2003.
 Exchange Server 2007
Exchange Server 2007 was released on November 30, 2006, to business customers as part of Microsoft’s roll-out wave of new products. It includes new clustering options, 64-bit support for greater scalability, voice mail integration, better search and support for Web services, better filtering options, and a new Outlook Web Access interface. Exchange 2007 also dropped support for Exchange 5.50 migrations, routing groups, admin groups, Outlook Mobile Access, X.400, and some API interfaces, amongst other features.
Exchange Server 2007 (v8, code name E12, or with SP1 v8.1) runs only on 64-bit x86-64 versions of Windows Server. This requirement applies to supported production environments only; a 32-bit trial version is available for download and testing. Hence, companies currently running Exchange Server on 32-bit hardware will be required to replace or migrate hardware if they wish to upgrade to the new version. Companies that are currently running Exchange Server on 64-bit capable hardware are still required to migrate from their existing Exchange 2000/2003 servers to a new 2007 server since in-place upgrades are not supported in 2007.
The first beta of Exchange Server 2007 (then named “Exchange 12” or E12) was released in December 2005 to a very limited number of beta testers. A wider beta was made available via TechNet Plus and MSDN subscriptions in March 2006 according to the Microsoft Exchange team blog. On April 25, 2006, Microsoft announced that the next version of Exchange Server would be called Exchange Server 2007.
Exchange server 2007 comes in two editions, Exchange Server 2007 Standard edition and Exchange Server 2007 Enterprise Edition. Standard edition can have 5 databases in up to 5 storage groups, while in Enterprise edition this is extended to 50 databases in up to 50 storage groups.
SCC and CCR is not supported in standard edition but LCR and SCR is supported. While in exchange 2007 enterprise edition SCC, LCR, CCR and SCR is supported.
Exchange Server 2007 is an integrated part of the Innovative Communications Alliance products.
 New features
The principal enhancements, as outlined by Microsoft, are:
- Protection: anti-spam, antivirus, compliance, clustering with data replication, improved security and encryption
- Improved Information Worker Access: improved calendaring, unified messaging, improved mobility, improved web access
- Improved IT Experience: 64-bit performance & scalability, command-line shell & simplified GUI, improved deployment, role separation, simplified routing
- Exchange Management Shell: a new command-lineshell and scripting language for system administration (based on Windows Power Shell). Shell users can perform every task that can be performed in the Exchange Server graphical user interface plus additional tasks, and can program often-used or complex tasks into scripts that can be saved, shared, and re-used. The Exchange Management Shell has over 375 unique commands to manage features of Microsoft Exchange Server 2007.
- “Unified Messaging” that lets users receive voice mail, e-mail, and faxes in their mailboxes, and lets them access their mailboxes from cell phones and other wireless devices. Voice commands can be given to control and listen to e-mail over the phone (and also send some basic messages, like “I’ll be late”)
- Increased the database maximum size limit. Database size is now limited to 16TB per database
- Increased the maximum number of storage groups and mail databases per server, to 5 each for Standard Edition (from 1 each in Exchange Server 2003 Standard), and to 50 each for Enterprise Edition (from 4 groups and 20 databases in Exchange Server 2003 Enterprise).
- You can configure Outlook Anywhere (formerly known as RPC over HTTP) to provide external access to Microsoft Exchange Server 2007 for your clients. If you want Microsoft Office Outlook 2007 user profiles to be automatically configured to connect to Exchange 2007, configure the Autodiscover service. This also provides external URLs for Exchange services such as the Availability service and offline address book.
Exchange Server 2010
Microsoft reached the RTM (Release To Manufacturing) milestone for Exchange Server 2010 on October 8, 2009, and was officially launched on November 9, 2009. A 120 day trial is downloadable from Microsoft. Exchange Server 2010 is available in two server editions; Standard edition and Enterprise edition.
Major changes from previous versions of Exchange Server include:
- The high availability options for Mailbox Databases (SCC: Single Copy Clustering, CCR: Clustered Continuous Replication and LCR: Local Continuous Replication) and site resiliency functionality (SCR: Standby Continuous Replication) have been replaced by Database Availability Groups (DAGs) in Exchange Server 2010. Major DAG benefits include providing database level high availability (as opposed to server level), support for up to sixteen (16) copies of each database, and flexible configuration (databases copies may be added / removed at will without requiring major server reconfiguration). Each server that runs the Enterprise edition of Exchange Server 2010 can host up to 100 database copies.
- High availability for the Client Access Server role in Exchange Server 2010 is provided by using Client Access Server (CAS) arrays. A CAS array can contain multiple Client Access Servers in an Active Directory site and provide a single name endpoint for client connections. CAS arrays cannot span multiple Active Directory sites.
- In Exchange Server 2007, a clustered mailbox server could not be combined with any other roles. In Exchange Server 2010, the Mailbox Server Role may be combined with the Client Access Server and/or Hub Transport roles, regardless of whether or not the mailbox server participates in a Database Availability Group. (However, since Database Availability Groups use Windows Failover Clustering, and Microsoft does not support the combination of Windows Failover Clustering and Windows Network Load Balancing on the same server, a multi-role deployment will require the use of a 3rd party load balancer to provide load balancing and fault tolerance for the Client Access Server role).
- With the introduction of the RPC Client Access service, all Outlook clients access their mailbox database through the Client Access Server role. This abstraction layer allows for improved load balancing and redundancy and minimal client impact in the event of a database level *-over (“switchover” or “failover”) event.
- Exchange Server 2010 provides cost savings in required hardware. Storage performance requirements (measured in IOPS: Input/Output operations Per Second) have been reduced by approximately 70% over Exchange Server 2007, and by approximately 90% over Exchange Server 2003. According to a case study, Microsoft IT was able to reduce hardware costs by 75% during the migration from Exchange Server 2007 to Exchange Server 2010.
- Exchange Server 2010 extends the large mailbox support introduced in Exchange Server 2007, and also introduces a Personal Archive feature to allow messages to be retained longer without the need for a 3rd party archival system. The Personal Archive is implemented as a secondary mailbox for archive-enabled users, and in Exchange Server 2010 Service Pack 1, the Personal Archive may be located on a different database than the primary mailbox, which may reside on a different disk if desired.
- The compliance and legal search features have been enhanced. What was formerly known as the “Dumpster” in previous versions of Exchange (a special storage area for messages which have been deleted from the Deleted Items folder or “permanently deleted” from a regular folder, such as the Inbox) has been evolved into the Recoverable Items folder in Exchange Server 2010. If configured appropriately, the Recoverable Items folder allows for a “tamper proof” storage area (users cannot circumvent the Recoverable Items folder to bypass legal discovery), which also provides a revision history of any modified items.
- Administration delegation can now be performed at a granular level due to Exchange Server 2010’s implementation of Role Based Access Control (RBAC). Users and administrators can be given extremely fine grained abilities for functions provided both within the Exchange Management Console or Exchange Management Shell and in Outlook Web App. For example, a compliance officer may be given the ability to perform cross mailbox discovery searches within Outlook Web App; a help desk technician may be granted the ability to set an Out Of Office message for other employees within the company, or a branch administrator in a remote office may be granted the permission to perform specific Exchange Management Shell commands that pertain only to the Exchange server in their branch office.
- Outlook Web App includes improvements (including, for example, the ability for users to track their sent messages and printable calendar views) and the “Premium” experience is now available across multiple browsers (including Safari and Firefox).
- Distribution groups can now be “moderated”, meaning that distribution groups can now be configured to allow users to join at will or only with a group moderator’s permission, and individual messages sent to distribution groups can now be approved or denied by a moderator.
- Exchange Server 2010 introduces a transport concept called “Shadow Redundancy” which protects e-mail messages while they are in transit. If a Hub Transport server or an Edge Transport server fails after it has received a message for processing, but before it was able to deliver it to the next “hop” server, the server which sent the message to that transport server is now able to detect the failure and redeliver the message to a different Hub Transport or Edge Transport server for processing.
In January 2011, Microsoft Exchange Server 2010 won InfoWorld’s 2011 Technology of the Year Award for Best Mail Server.
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 physical 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 ISV’s 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 datacenters 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 you add a Mailbox server 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, you can choose to use User or Device CALs. Device CALs are assigned to a device (workstation, laptop or PDA). User CALs, are assigned to a user or employee (not a mailbox). User CALs allow a user to access Exchange e-mail from any device. User and Device CALs are the same price, however cannot be used interchangeably. For Service Providers looking to host Microsoft Exchange, there is an SPLA (Service Provider License Agreement) available whereby Microsoft receives a monthly service fee in the place of the traditional Client Access Licenses. 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 can also be purchased as a hosted service from a number of providers.
Microsoft Exchange Server uses a proprietary RPC protocol, MAPI/RPC, that was designed to be used by the Microsoft Outlook client. Clients capable of using the proprietary features of Exchange Server include Microsoft Outlook and Novell Evolution. 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 vs. WebDAV, which is used by Exchange Server 2003. Exchange Web Services is used by the latest version of Microsoft Entourage for Mac. Also, since the release of Mac OS X v10.6 (also known as 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.
Mac users wishing to access Exchange e-mail running on Exchange Server 2000 or 2003 must use Microsoft’s Entourage client versions X, 2004 or 2008. Alternatively a limited version of Outlook Web Access is available to Mac users using a web browser. Entourage X, 2004 and 2008 do not support synchronizing tasks and notes with Exchange Servers 2000, 2003, 2007 or 2010. However Entourage 2008 “Web Services Edition”, which is a free download from Microsoft for users of Office 2008, does support synchronizing tasks and notes with Exchange Server 2007 SP1 rollup update 4 or later (including Exchange 2010).
E-mail hosted on an Exchange Server can also be accessed using SMTP, POP3 and IMAP4 protocols, using clients such as Outlook Express, Mozilla Thunderbird, and Lotus Notes. (These protocols must be enabled on the server. Recent versions of Exchange Server turn them off by default.)
Exchange Server mailboxes can also be accessed through a web browser, using Outlook Web Access (OWA), called Outlook Web App in Exchange Server 2010. Exchange Server 2003 also featured a version of OWA for mobile devices, called Outlook Mobile Access (OMA).
DavMail Gateway allows any email client to connect to a Microsoft Outlook server with Outlook Web Access (OWA).
GNOME Evolution project can be used to Connect to MS-Exchange (in OWA mode for Exchange 2000/2003, native mode for Exchange 2007). Evolution is now also available for Windows.
Support for Exchange ActiveSync was added to Microsoft Exchange Server 2003. Exchange ActiveSync, in the context of Exchange Server, allows a compliant device such as a Windows Mobile device to securely synchronize mail, contacts and other data directly with an Exchange server. Since its inception, ActiveSync has become a popular mobile access standard for businesses due to cross-platform support from companies like Nokia and Apple Inc. as well as its advanced device security and compliance features.
Support for Push E-mail was added to Exchange Server 2003 with Service Pack 2. Windows Mobile 5.0 requires the “Messaging and Security Feature Pack (MSFP)”, later versions of the mobile operating system, such as Windows Phone 7, have the capability built in. Many other devices now support ActiveSync push e-mail, such as the iPhone and Android Phones.
Exchange Server 2007 and Exchange Server 2010 support the use of Exchange ActiveSync Policies. By using Exchange ActiveSync Policies, administrators can secure the devices that connect to the organization or remotely deactivate features on the devices. Administrators or users can also remotely wipe a lost mobile device.
Source: http://en.wikipedia.org/wiki/Microsoft_Exchange_Server#cite_note-27 (wikipedia)