Overview of Exchange ActiveSync

Smartphone synchronization software has been released by Microsoft under the name ActiveSync since 1996, including the forerunner to today's Exchange ActiveSync, released as part of the Mobile Information Server 2002 product. However, it wasn't until the release of Exchange Server 2003 SP2, back in 2005, that it bore a resemblance to its current form today. Version 2.5 was the first version to support the modern features, such as push-e-mail and mail, calendar, contact, and task synchronization, along with a basic set of security features.

With the release of Exchange Server 2007, and later Exchange Server 2007 Service Pack 1, a large number of device management and security policies were incrementally added, and in the current release of Exchange Server 2010 the full complement of features are available, including those related to conversation view (message threading).

Exchange ActiveSync works by using features built into HTTP (Hypertext Transport Protocol, as used by web sites) to allow the mobile device to ask the server, over a secure connection, to let it know when there is an update. It works by issuing a request to the Exchange Server and when there is a change, such as a new e-mail, the server replies to that request with an update. This allows push-email over a normal mobile data connection such as 2G/3G without excessive data and battery usage.

The following diagram shows this process:

Exchange ActiveSync, although a proprietary protocol has been licensed by a number of other server products and helped by support from smartphones like the Apple iPhone, is becoming one of the most common ways to support push mail. Exchange ActiveSync has been licensed by other mail server products in addition to Exchange Server and Office 365. The following are just a few examples:

Nonetheless, there are other options for synchronizing and delivering push e-mails to Smartphones. Most people have heard of the Blackberry, which was one of the first providers to allow push e-mail to their mobile devices using their proprietary Blackberry Enterprise Server, and it's clear that the rising popularity of the product inspired Microsoft to develop the Exchange ActiveSync protocol further.

Another well-known option is Good Technologies' cross-platform mobile synchronization product, which includes support for the iPhone. Often used in some of the most secure environments it offers a full end-to-end solution, including a custom Mail application for the iPhone and server-side software.

For most purposes though, Exchange ActiveSync is more than capable and with broad device support, including great support from Apple for the iOS range of devices, it is often an easy choice to make, thanks to the out-of-the-box support it provides.