Exchange ActiveSync Overview



This Exchange TechNet Wiki page contains information about the history of the Exchange ActiveSync (EAS) server and client protocol.

Table of Contents




Exchange ActiveSync (EAS) is an XML Jump -based protocol that is designed for the synchronization of email, contacts, calendar, and tasks from a messaging server to a mobile device. The protocol also provides mobile device management Jump and policy controls.


Exchange ActiveSync 1.0

The first version of Exchange ActiveSync (called AirSync at the time) was a part of Microsoft Information Server (MIS) 2002. This version of EAS communicated over Web-based Distributed Authoring and Versioning (WebDAV Jump ) 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 calendar). 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

Exchange ActiveSync (EAS) 2.0 shipped in Exchange Server Jump 2003. 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 & contacts folders.  Always Up To Date (AUTD) was implemented as a way to let a device know if there was new information for it and Short Message Service (SMS Jump ) 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

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 Jump ) to 1:X short IDs for all items which reduced the amount of data sent across the wireless network.

Exchange ActiveSync 2.5

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 Jump ) 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 as added as was S/MIME Jump email encryption and the following policies 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

Exchange ActiveSync (EAS) 12.0 came with Exchange Server 2007. EAS 12.0 was a complete re-write of the protocol (in managed code Jump ) from its previous version. New features included password reset which allowed users to reset a forgotten PIN lock code, HTML Jump email (previously email was all in plain text), 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. 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 Jump access
  • Encrypt storage card

Exchange ActiveSync 12.1

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 Jump 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:

  • Disable desktop ActiveSync
  • Disable removable storage
  • Disable camera
  • Disable SMS text messaging
  • Disable Wi-Fi Jump
  • Disable Bluetooth
  • Disable IrDA
  • Allow internet sharing from device
  • Allow desktop sharing from device
  • Disable POP3 Jump /IMAP4 Jump email
  • Allow consumer email
  • Allow 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

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 Jump ) 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 Jump ) 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 they were aware of an updated version of the client that would enable newer features.

Exchange ActiveSync 14.1

Exchange ActiveSync (EAS) 14.1 came as part of Exchange Server 2010 SP1. This version of the protocol added GAL photo (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 Jump ) 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 Jump in 2007. The protocol licensing continued until 2008.

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


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 Jump 


Compatibility: implementation


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. A compatibility list has been posted online that helps those interested see which features are implemented in which phones. 

Desktop ActiveSync

Desktop ActiveSync Jump (Windows 95, 98, XP, 2000) was a desktop application designed to synchronize and set up Windows Mobile devices though a connection (USB, Wi-Fi, Bluetooth, IR) to a computer. This varies greatly from Exchange ActiveSync which is a wireless synchronization protocol. The desktop application 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). Since the names were so similar, ActiveSync (the desktop application) has changed its name to Windows Mobile Device Center (WMDC Jump ).  


  1. ^ "Exchange ActiveSync and Exchange 2003" Jump . Retrieved July 7, 2010. 
  2. ^ "Exchange ActiveSync and Exchange 2003" Jump . Retrieved July 7, 2010. 
  3. ^ "Exchange ActiveSync and Exchange 2003" Jump . Retrieved July 7, 2010. 
  4. ^ "New Mobility Features in Exchange Server 2003 SP2" Jump . Retrieved July 7, 2010. 
  5. ^ "Overview of Exchange ActiveSync" Jump . Retrieved July 7, 2010. 
  6. ^ "Understanding Exchange ActiveSync Mailbox Policies" Jump .  Retrieved July 7, 2010. 
  7. ^ "Microsoft and Xandros Expand Collaboration" Jump . Retrieved July 7, 2010. 
  8. ^ "Microsoft Expands Exchange ActiveSync Licensing Program" Jump . Retrieved July 7, 2010.

External links