EAS: King of Sync?

Seven months or so ago, IBM surprised a bunch of people by announcing that they were licensing Microsoft’s Exchange ActiveSync protocol (EAS) for use with a future version of Lotus Notes. I’m sure there were a few folks who saw it coming, but I cheerfully admit that I was not one of them. After about 30 seconds of thought, though, I realized that it made all kinds of sense. EAS is a well-designed protocol, I am told by my developer friends, and I can certainly attest to the relative lightweight load it puts on Exchange servers as compared to some of the popular alternatives – enough so that BlackBerry add-ons that speak EAS have become a not-unheard of alternative for many organizations.

So, imagine my surprise when my Linux geek friend Nick told me smugly that he now had a new Palm Pre and was synching it to his Linux-based email system using the Pre’s EAS support. “Oh?” said I, trying to stay casual as I was mentally envisioning the screwed-up mail forwarding schemes he’d put in place to route his email to an Exchange server somewhere. “Did you finally break down and migrate your email to an Exchange system? If not, how’d you do that?”

Nick then proceeded to point me in the direction of Z-Push, which is an elegant little open source PHP-based implementation of EAS. A few minutes of poking around and I became convinced that this was a wicked cool project. I really like how Z-Push is designed:

  • The core PHP module answers incoming requests for the http://server/Microsoft-Server-ActiveSync virtual directory and handles all the protocol-level interactions. I haven’t dug into this deeply, but although it appears it was developed against Apache, folks have managed to get it working on a variety of web servers, including IIS! I’m not clear on whether authentication is handled by the package itself or by the web server. Now that I think about it, I suspect it just proxies your provided credentials on to the appropriate back-end system so that you don’t have to worry about integrating Z-Push with your authentication sources.
  • One or more back-end modules (also written in PHP), which read and write data from various data sources such as your IMAP server, a Maildir file system, or some other source of mail, calendar, or contact information. These back-end modules are run through a differential engine to help cut down on the amount of synching the back-end modules must perform. It looks like the API for these modules is very well thought-out; they obviously want developers to be able to easily write backends to tie in to a wide variety of data sources. You can mix and match multiple backends; for example, get your contact data from one system, your calendar from another, and your email from yet a third system.
  • If you’re running the Zarafa mail server, there’s a separate component that handles all types of data directly from Zarafa, easing your configuration. (Hey – Zarafa and Z-Push…I wonder if Zarafa provides developer resources; if so, way to go, guys!)

You do need to be careful about the back-end modules; because they’re PHP code running on your web server, poor design or bugs can slam your web server. For example, there’s currently a bug in how the IMAP back-end re-scans messages, and the resulting load can create a noticeable impact on an otherwise healthy Apache server with just a handful of users. It’s a good thing that there seems to be a lively and knowledgeable community on the Z-Push forums; they haven’t wasted any time in diagnosing the bug and providing suggested fixes.

Very deeply cool – folks are using Z-Push to provide, for example, an EAS connection point on their Windows Home Server, synching to their Gmail account. I wonder how long it will take for Linux-based “Exchange killers” (other than Zarafa) to wrap this product into their overall packages.

It’s products like this that help reinforce the awareness that EAS – and indirectly, Exchange – are a dominant enough force in the email market to make the viability of this kind of project not only potentially useful, but viable as an open source project.

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