Exchange ActiveSync

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Not to be confused with ActiveSync.
Microsoft Exchange ActiveSync
Exchange ActiveSync.png
Developer(s) Microsoft
Initial release 2002 (2002)
Stable release 14.0 / October 8, 2009; 5 years ago (2009-10-08)
Development status Active
Type Wireless messaging/PIM sync and management protocol
License Proprietary

Microsoft Exchange ActiveSync (commonly known as EAS) is a protocol designed for the synchronization of email, contacts, calendar, tasks, and notes from a messaging server to a smartphone or other mobile device. The protocol also provides mobile device management and policy controls. The protocol is based on XML and the Exchange ActiveSync server and the mobile device communicate over HTTP or, more commonly, HTTPS. Originally branded as AirSync and only supporting Microsoft Exchange Servers and Microsoft Pocket PC devices, the protocol has since become a de facto standard[1] for synchronization between groupware and mobile devices.

Microsoft licenses the technology, and support for Exchange ActiveSync is now implemented in a number of competing collaboration platforms, including GroupWise with the Novell Data Synchronizer Mobility Pack software and Lotus Notes with IBM Notes Traveler. Google previously offered support for the protocol for personal Gmail and free Google Apps accounts, but began removing support from all but paid Google Apps for Business subscriptions in 2013.[2] Beyond on premises installations of Exchange, the various personal and enterprise hosted services from Microsoft also utilize Exchange ActiveSync, including and Office 365.

In addition to support on Windows Phone, Exchange ActiveSync client support is included on Android,[3] iOS,[4] BlackBerry 10 smartphones and the BlackBerry PlayBook tablet computer. The built-in email application for Windows 8 desktop, Mail app, also supports the protocol.[5]


Exchange ActiveSync 1.0[edit]

The first version of Exchange ActiveSync (called AirSync at the time) was a part of Mobile Information Server (MIS) 2002.[6] This version of EAS communicated over Web-based Distributed Authoring and Versioning (WebDAV) to Exchange 2000 servers syncing Email, contacts, and calendar and allowed users to select a folder list to sync but this was only for email folders (not contacts or calendars). This initial version of EAS has the user’s device “pull” data down rather than have the server “push” new information as soon as it was available.

Exchange ActiveSync 2.0[edit]

Exchange ActiveSync (EAS) 2.0 shipped in Exchange Server 2003.[6] This version of the protocol was developed by the Microsoft Windows Mobile team and was delivered as a binary drop (massync.dll) to the Exchange Server team. Exchange ActiveSync used WebDAV to connect to a user's mailbox and added the ability to sync non-default calendar and contacts folders. Always Up To Date (AUTD)[6] was implemented as a way to let a device know if there was new information for it and Short Message Service (SMS) was the technology used to deliver this information to the device. Because of the use of SMS as a notification, the configuration of an SMS gateway was required and each account needed to be configured with a user's mobile phone number.

Exchange ActiveSync 2.1[edit]

In Exchange Server 2003 SP1 ghosting support was added to Exchange ActiveSync 2.1. Ghosting tells server what they can sync and then all is sent down but when changes are sent up, only specified fields are changed (others are not deleted). The Exchange ActiveSync protocol also moved from a Globally Unique Identifier (GUID) to 1:X short IDs for all items which reduced the amount of data sent across the wireless network.

Exchange ActiveSync 2.5[edit]

Exchange ActiveSync 2.5 (Part of Exchange Server 2003 SP2) was the first version of Exchange ActiveSync to be written by the Exchange Server team. This version also introduced Direct Push (a real-time push e-mail solution which allows the server to say “I have a new item for you” and then tells the client device to do a sync (this was called a “Ping Sync”)). Global Address List (GAL) search was added to enable people to look up other co-workers in their company directory to find their email address. The ability to remotely wipe a device was also added so administrators could remove company data from a device that was lost, stolen, or after an employee left the company. Tasks syncing was added as was S/MIME email encryption and the following policies[7] were added:

  • Minimum password length
  • Timeout without user input
  • Require password
  • Require alphanumeric password
  • Number of failed attempts
  • Policy refresh interval
  • Allow non-provisionable device

Exchange ActiveSync 12.0[edit]

Exchange ActiveSync (EAS) 12.0 came with Exchange Server 2007. EAS 12.0 was a complete re-write of the protocol (in managed code) from its previous version. New features included password reset which allowed users to reset a forgotten PIN lock code, message flagging which gave users the ability to mark a message so they could remember to follow up on it when they got back to their computer, Out of Office setting so users could set an “away” message from their phone, SharePoint (and UNC file share) access from links in email (file traffic was proxied though EAS), Empty deleted items to allow people to shrink their mailboxes so they didn’t exceed their mailbox size limits, fetch which allowed users to get only parts of a message and then choose later to get the rest of the message (or an attachment) later, device info which allowed users and administrators to see which phones were connected to their accounts, and AutoDiscover which (although strictly speaking isn’t part of the EAS protocol) allowed phones to automatically configure the EAS connection with just a user login and password (instead of requiring people to know the computer name of their Exchange Server). The ability to see who was invited to a meeting was also added as well as the ability to search the server for an email that was not synced to the device.[8] The new policies introduced were:

  • Allow attachment download
  • Maximum attachment size
  • Enable password recovery
  • Allow simple password
  • Password expiration (Days)
  • Enforce password history
  • Windows file share access
  • Windows SharePoint access
  • Encrypt storage card

Exchange ActiveSync 12.1[edit]

Exchange ActiveSync (EAS) 12.1 came in Exchange Server 2007 SP1. This version of the protocol was one of the largest changes since version 2.5 and featured header compression (Base64 encoding of a binary structure) to decrease the amount of data sent wirelessly, Multiple collections sync (a bundling of all sync requests together instead of the previous way of doing a sync for each folder separately), a hanging sync which allowed the server to keep a communications channel open to the client at all times so battery life and data wouldn’t be consumed constantly turning on the radio and querying the server and was a “true push sync” solution (which had far lower message delivery latencies, as opposed to the previous ping based “push to pull” solution), a confirmation of a completed remote wipe, as well as the following 30 new policies:[9]

  • Disable desktop ActiveSync
  • Disable removable storage
  • Disable camera
  • Disable SMS text messaging
  • Disable Wi-Fi
  • Disable Bluetooth
  • Disable IrDA
  • Allow internet sharing from device
  • Allow desktop sharing from device
  • Disable POP3/IMAP4 email
  • Allow consumer email
  • Allow web browser
  • Allow unsigned applications
  • Allow unsigned CABs
  • Application allow list
  • Application block list
  • Require signed S/MIME messages
  • Require encrypted S/MIME messages
  • Require signed S/MIME algorithm
  • Require encrypted S/MIME algorithm
  • Allow S/MIME encrypted algorithm negotiation
  • Allow S/MIME SoftCerts
  • Device encryption
  • Minimum number of complex characters
  • Configure message formats (HTML or plain text)
  • Include past email items (duration)
  • Email body truncation size
  • HTML email body truncation size
  • Include past calendar items (duration)
  • Require manual sync when roaming

Exchange ActiveSync 14.0[edit]

Exchange ActiveSync 14.0 was introduced as part of Exchange Server 2010. This new version added a new conversation view that put email messages in a view connected by several attributes including a Message-ID and the email subject, notes syncing, the ability to look up the availability (free/busy status) of a contact (from their calendar), a Nickname Cache which shared the names of common used contacts between Outlook Web App (OWA) and EAS, the ability to set a server side rule to always move messages in a conversation, lunar calendar support, syncing of the reply state (which let the device and the server know if any message had been forwarded or replied to from any other source), a new way to identify Unified Messaging (UM) messages so that voicemail that appeared in a user’s inbox could be handled differently, SMS Syncing (which allowed users to see their SMS messages in their email inbox and reply to them from their inbox instead of on their phone), and the following two new policies:

  • Allow Mobile OTA Update
  • Mobile OTA Update Mode

This is also the first version of EAS that identified clients that were using older versions of EAS and alerted them if there was an updated version of the client that would enable newer features.

Exchange ActiveSync 14.1[edit]

Exchange ActiveSync (EAS) 14.1 came as part of Exchange Server 2010 SP1. This version of the protocol added GAL photos (images stored in an Active Directory server of the user who has sent the email), Message Diffs (a means of sending only the new portion of an email and avoiding redundant information), added device/user information to the provision command so that the new Allow/Block/Quarantine feature could more easily allow administrators to control which devices connected to their organizations, and Information Rights Management (IRM) over EAS (a method to apply digital rights management control and encryption to email messages that are sent and received). The following is the one new policy that was added in EAS 14.1:

  • Allow IRM over EAS


Beginning in the early 2000s, Exchange ActiveSync (EAS) began to be available for licensing. At the time it was a client only protocol license. Motorola was the first licensee and began with a license of the 2.1 version of EAS. Various other organizations licensed EAS over time and Microsoft eventually started licensing the server side of EAS in 2007.[10] The protocol licensing continued until 2008.

In December 2008 Microsoft shifted its licensing of Exchange ActiveSync from that of a protocol license, to licensing the patents of Exchange ActiveSync[11] and providing full protocol documentation.[12]

Google uses an implementation of Exchange ActiveSync for its Google Apps for Business subscribers. Likewise, IBM and Novell have implemented the technology to allow their competing groupware servers (Lotus Domino and Novell GroupWise) to support smartphones and other devices, through IBM Notes Traveler and Novell Data Synchronizer Mobility Pack, respectively.


Exchange ActiveSync began being licensed in the early 2000s to mobile device manufactures. The current list of licensees is located on the Microsoft Intellectual Property licensing page.[13] A feature comparison chart shows different features available from the various EAS clients.


Exchange ActiveSync (EAS) has iterated though several versions (from 1.0 to 14.1). Because EAS is licensed as a series of patents (and not given as computer code to other companies), different clients and servers implement a subset of the entire features of the protocol and the implementations are written by each company that has obtained a license.

Logo program[edit]

In April 2011, Microsoft launched the Exchange ActiveSync logo program,[14] which tests third-party EAS clients in mobile email devices. Handset manufacturers that have licensed the EAS protocol from Microsoft are eligible to join the program. In order to be compliant, EAS clients must employ EAS v14.0 or later and enable the following features and management policies:

  • Direct Push email, contacts and calendar
  • Accept, decline and tentative accept meetings
  • Rich formatted email (HTML)
  • Reply/forward state on email
  • GAL lookup
  • Autodiscover
  • Allow-Block-Quarantine strings for device type and device model
  • Remote wipe
  • Password required
  • Minimum password length
  • Timeout without user input
  • Number of failed attempts

Desktop apps[edit]

ActiveSync was a desktop application designed to synchronize and set up Windows Mobile devices through a USB, Wi-Fi, Bluetooth or IrDA connection to a computer.[15] It is capable of syncing with Outlook on the desktop but not syncing wirelessly from the device to the email server (though it can configure these settings). ActiveSync is replaced by Windows Mobile Device Center (WMDC).

See also[edit]


  1. ^ Notify Technology Unveils On-Demand Mobile Device Management. PCWorld. Retrieved on 2013-10-23.
  2. ^ Google Extends Exchange ActiveSync Support for Gmail. Retrieved on 2013-10-23.
  3. ^
  4. ^ Apple adds Exchange support to iPhone, unveils SDK. Computerworld (2008-03-06). Retrieved on 2013-10-23.
  5. ^ Mail app for Windows - Microsoft Windows. Retrieved on 2013-10-23.
  6. ^ a b c "Exchange ActiveSync and Exchange 2003". Retrieved July 7, 2010. 
  7. ^ "New Mobility Features in Exchange Server 2003 SP2". Retrieved July 7, 2010. 
  8. ^ "Overview of Exchange ActiveSync". Retrieved July 7, 2010. 
  9. ^ "Understanding Exchange ActiveSync Mailbox Policies". Retrieved July 7, 2010. 
  10. ^ "Microsoft and Xandros Expand Collaboration". Retrieved July 7, 2010. 
  11. ^ "Microsoft Expands Exchange ActiveSync Licensing Program". Retrieved July 7, 2010. 
  12. ^ "Exchange ActiveSync protocol documentation". MSDN. Retrieved 19 November 2012. 
  13. ^ "Exchange ActiveSync Protocol". Legal and Corporate Affairs. Microsoft. Retrieved 19 November 2012. 
  14. ^ "Exchange ActiveSync logo program". Microsoft TechNet. Microsoft. Retrieved 19 November 2012. 
  15. ^ "ActiveSync 4.5". Download Center. Microsoft. 13 February 2007. Retrieved 19 November 2012. 

Further reading[edit]

  1. "Exchange ActiveSync: Frequently Asked Questions". Microsoft Exchange Server TechCenter. Microsoft Corporation. 2012. Retrieved 2012-11-23. 
  2. "Exchange ActiveSync". Microsoft TechNet. Microsoft. 5 October 2012. Retrieved 19 November 2012. 
  3. "Mobile Email with Exchange ActiveSync". Microsoft Exchange portal. Microsoft. Retrieved 19 November 2012. 
  4. "Exchange ActiveSync Overview". TechNet Wiki. Microsoft. Retrieved 19 November 2012. 
  5. "Exchange ActiveSync Client Comparison Table". TechNet Wiki. Microsoft. Retrieved 19 November 2012. 
  6. "New to Exchange ActiveSync Development?". MSDN Blog. Microsoft. Retrieved 28 November 2012. 
  7. "Exchange Server Protocol Documents". MSDN Documentation. Microsoft. Retrieved 28 November 2012. 
  8. "Exchange Server Interoperability Guidance". Exchange Server - Dev Center. Microsoft. Retrieved 28 November 2012.