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Lemonade Mobile E-Mail Profile


Lemonade provides a standards-based approach to mobilizing IMAP and SMTP e-mail clients. This would let consumers and businesses break out of the proprietary models offered by mobile e-mail providers such as Motorola, Nokia, RIM and Sybase.

Lemonade is being developed by a working group of the IETF, represented by Alcatel-Lucent, Cantata Technology, Cingular Wireless, Comverse, Isode, Nokia, Nortel Networks, Oracle, Qualcomm, Sprint Nextel and Sun Microsystems. Expect vendors of IMAP-compliant mail servers to integrate the Lemonade profile into their products over time.

By offering a cost-effective, standards-based approach to both mobile carriers and service providers, Lemonade has the potential to bring mobile e-mail to a wider array of consumers, though its adoption will be hampered by its lack of clients built with Lemonade in mind, and it doesn't address the range of corporate mobile applications that RIM's BlackBerry does, for example. In the future, mobile e-mail will become a much more common messaging technology, eclipsing SMS messaging.

A year ago, a legal ruling against BlackBerry maker Research in Motion highlighted the need for a standards-based approach to mobile e-mail. And though RIM settled the case soon after the ruling and retained the ability to sell BlackBerry services and devices, the need for standardization remains.

Now, a working group from the IETF, Internet E-Mail to Support Diverse Service Environments (aka Lemonade), is making strides toward a true standard for mobile e-mail. The group's Lemonade spec, sometimes referred to as Push IMAP, draws on existing parts of the IMAP4 and SMTP profiles (a collection of standards), and delivers new RFCs for a unified approach to mobile e-mail services, where messages are automatically pushed to a mobile device and sync'd with a user's e-mail server.

Enterprises will be attracted to the Lemonade profile since it will hedge against vendor lock-in. With a standards-based approach, more players, including ISVs, service providers and carriers, will be able to provide mobile e-mail services. And more choices will help drive down the cost of services as products mature.

However, many mobile e-mail products, such as RIM's, have extended beyond e-mail to enterprise applications and access to corporate data; Lemonade addresses a standard only for mobile e-mail. Companies with such systems must weigh the cost and effort of switching against the benefits of a new standards-based implementation that isn't integrated with other mobile apps. And with limited e-mail server and client support, it may be a while before Lemonade takes hold. Look for existing vendors like RIM to continue their focus on mobile access to corporate data, mobile applications, management and other features to provide differentiation as mobile e-mail becomes further commoditized.

Building On IMAP4, SMTP

The Lemonade working group, consisting of vendors such as Alcatel-Lucent, Cingular Wireless, Nokia, Nortel Networks, Oracle, Qualcomm, Sprint Nextel and Sun Microsystems, published the Lemonade profile in February 2006. It extends IMAP4, which defines the receiving of messages, management of e-mail boxes, checking for messages and so on, as well as SMTP, which defines how to send e-mail.

Push e-mail functionality is handled through the IMAP IDLE command established in RFC 2177. This command opens a connection to the IMAP server and, as the name implies, leaves the connection idle. If new messages arrive, the IMAP server informs the client over the idle connection. The connection is kept persistently open using the NOOP (no operation) command, which is issued roughly every 15 minutes. The NOOP command tells the IMAP server to issue an OK reply, thus resetting any factors that may cause the idle connection to time out.

There are several new enhancements that boost IMAP4's efficiency and robustness under mobile conditions, most notably in the area of resynchronization. Standard IMAP4 clients are resource-intensive in synchronizing the mailbox with the server; a standard client will recheck the entire mailbox on the server in order to synchronize the mailbox on the client device.

The Lemonade profile handles this with RFC 4551, a "conditional STORE" extension to IMAP, which will check only for changes that have occurred since the last synchronization, rather than rebuilding the entire mailbox. An efficient synchronization method is important because mobile connections can be broken and re-established many times in a given session, causing the mailbox to have to be resynchronized with each new connection.

The Lemonade profile also offers a new feature called "forward without download." Traditionally, to forward a message to another user, the message first must be downloaded to the client PC and then sent as a new message through an SMTP server. The extension lets a user forward a message without downloading it to the mobile device. Other extensions deal with efficiency and performance: The Lemonade profile adds transport-layer security (TLS, already found in IMAP4) to secure outgoing messages as well as compress messages for more efficient transport.

To take advantage of the Lemonade feature set, enterprises and service providers will have to move to e-mail servers and clients that are compatible with the Lemonade profile. Currently, there are a limited number of e-mail servers that support Lemonade, including Sun's Java System Messaging Server, Isode's M-Box and Cyrus IMAP (an open-source IMAP server maintained by Carnegie Mellon University). Where Lemonade is truly lacking is in client support. The cult-popular Chatteremail for PalmOS, along with a few others, have openly committed to supporting Lemonade. However, there have not been public commitments from such popular server platforms as Microsoft Exchange or Lotus Notes, nor from clients such as Microsoft Outlook or Palm Versa Mail.

With limited e-mail server and client support, the Lemonade profile will not make a big impact in the near future. Longer term, Lemonade's impact will likely be felt in the consumer market. Today, mobile carriers and even some e-mail providers push e-mail to consumers using proprietary software from companies such as Nokia and Seven Networks. However, the Lemonade profile should allow for greater competition, giving service providers and mobile carriers a cost-effective way to deliver mobile e-mail services. Many mobile phones, even non-smartphones like the Motorola RAZR, have basic IMAP4 clients. When the Lemonade profile is finalized, an increasing number of compliant servers and clients should become available. And as Lemonade is integrated into more IMAP4-compatible clients, mobile e-mail will morph from a mobile pro's favorite feature to a mature service enjoyed by consumers, much like SMS (Short Message Service).

For the enterprise market, the impact of the Lemonade profile is less clear. Some organizations may push to implement mobile standards to avoid vendor lock-in. However, Lemonade only addresses mobile e-mail; other features such as directory lookup, calendar and PIM synchronization are not addressed. There are standards for these features, primarily through SyncML (Synchronization Markup Language), but enterprises would have to look hard for vendors that offer both Lemonade and SyncML products; this may change over the next year as the profile is finalized.

Enterprises also should consider application mobilization as part of their long-term mobile strategy. Mobile e-mail vendors have begun to market solutions for mobilizing applications in addition to e-mail; application mobilization is possible through standards like SyncML.

In the future, enterprises must assess both standards-based and proprietary solutions; many proprietary solutions still have broad cross-platform support for both clients and servers. Factors such as cost, feature set and ROI should weigh more heavily than the proprietary vs. standards-based model. However, the development of standards in the mobile e-mail and application space will help drive down costs and drive up innovation just as the 802.11 standards did for WLAN technology. Don't take any action toward the Lemonade standard at least until Q4 2007; by then we hope to see more commitment from vendors as the standard nears finalization.

Sean Ginevan is a technology analyst with the center for Emerging Network Technologies at Syracuse University.