Push Email is a generic term for technologies used to keep email on mobile devices up-to-date with an Email Server-that is, new emails received by the server will be “immediately” notified to, and available on the device. In fact the term often encompasses technologies to push all PIM (Personal Information Management) data-for example, contacts and calendar (appointment) information-but email is the primary driving force for this important enterprise application and shall remain the focus in this article.

There are many solutions available (and more in development!) and each uses a slightly different approach. However, most mobile solutions do not use a true push-model but employ a “notify and pull-model” that typically follows these steps:
  When a new email (or other PIM update) arrives at the server, a notification is sent to any registered device(s). The device(s) may be permanently connected to the server over an IP (Internet Protocol)-based connection, or out-of-band notification may be used-such as SMS.
  The mobile device then pulls down the content from the server. Again the exact details will differ from solution to solution:

• Some solutions may just pull down the headers or a limited amount of body data in order to minimise the amount of data transferred or storage required, or to guarantee response times. In this case the user can typically pull down the rest of the information manually later.
• Alternatively the full email body may be pulled down, but full attachments are often not automatically transferred due to their unpredictable size (they can quickly fill the available disk space of a mobile device) and content (there might not be an application on the mobile device that can handle this type of file).

Of course, it is also possible to send emails from a device and each of these solutions will also allow this.

Further available solutions use an extended synchronisation method, whereby the receiving of an email at the server causes notification that a synchronisation is required-pushing a synchronisation request that pulls down the email rather than pushing the email directly.

An advantage of this type of solution is that it is possible to use a scheduled or manual synchronisation instead of the always-connected configuration when reception is poor, or to save data transfer outside of office hours or when roaming (not connected to your “home” network-for example, when abroad). A disadvantage is that it is a little more bandwidth hungry as extra synchronisation information is passed back-and-forth between the server and the device!

Obviously it is also possible to create a permanently-connected solution which does indeed push full emails to a device, but this is less flexible than a “notify and pull-model” and so is unlikely to be used until such time as network price rates reduce, network speeds increase and device storage increases.

Related Functionality

An important feature appearing in some solutions is the ability to remotely look up global information stored on the PIM server without having to store a complete copy of this data on the device. For example, you may wish to search your company's corporate contact database for all people called “Smith” in order to find the first name and phone number of a particular client. The ability to perform this type of search without having to synchronise every contact to your device (and let's face it-they might not all fit!) may well be an important feature separator for the mobile professional when deciding on which solution to go with.

The Future

As for the future - there are many Push Email systems currently available, but it is difficult at this time to determine which will become the most popular. Some solutions have very high profile brand names; some can integrate with a number of back-end servers through a plug-in architecture, such as Microsoft Exchange, Lotus Domino and IMAP/POP3 and some can integrate directly with existing servers without the need for extra back-end integration.

In the end it is likely to come down to a combination of cost, reliability, available feature set and ease of set-up and maintenance that will sway IT decision makers one way or the other.

About EMCC Software Limited

EMCC Software is a leading Symbian, Series 60 and UIQ Competence Center, providing software development services and solutions to the mobile industry. They have been working closely with Symbian and the device manufactures for over seven years, helping to develop the Symbian OS platform, mobile phones and innovative applications and solutions. Building on their reputation for technical excellence, EMCC has recently received accredited certification against the ISO9001:2000 standard and TickIT Guidelines Issue 5. Further information about EMCC Software Ltd and the services they offer can be found at www.emccsoft.com.