Exchange ActiveSync (commonly known as EAS) is a proprietary protocol by Microsoft, designed for the synchronization of email, contacts, calendar, tasks, and notes from a messaging server to a smartphone or other mobile devices.
Originally branded as AirSync and only supporting Microsoft Exchange Servers and Pocket PC devices, Microsoft now licenses the technology widely for synchronization between groupware and mobile devices in a number of competing collaboration platforms, including: In addition to support on Windows Phone, EAS client support is included on: Beyond on premises installations of Exchange, the various personal and enterprise hosted services from Microsoft also utilize EAS, including Outlook.com and Office 365.
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.
EAS used WebDAV to connect to a user's mailbox and added the ability to sync non-default calendar and contacts folders.
The EAS 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.
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).
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: 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.
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).
This version of the protocol contains three major capabilities: improved keyword search, propose new time and account-only remote wipe.