Messaging and Directory Server software used around the world in the Government, Military, Aviation and Commercial sectors.
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Isode's whitepapers are licenced under a Creative
Commons Licence.
17th November 2006
Purpose
LEMONADE is the Internet Standard for Mobile Email, based on IMAP and SMTP, described in the Isode White Paper LEMONADE Profile: The Key Standard for Mobile Messaging. This paper compares LEMONADE's approach to handling and delivering email and email attachments to mobile devices with that of the well known and widely deployed BlackBerry system.
What is BlackBerry and What is Being Compared?
The BlackBerry system was the first widely deployed mobile email solution. Its wide adoption and high profile are testament to the quality of the overall solution, which comprises:
- Server Software
- Client/Server protocol
- Client Hardware and associated OS
- Client Software
- Management Tools
- Wireless network integration
There are two distinct types of BlackBerry Deployment, with some common elements:
- BlackBerry Enterprise Service (BES). BES is designed for corporate email deployments, and may be used in conjunction with either Microsoft Exchange or Lotus Notes.
- BlackBerry Internet Service (BIS). BIS is designed for use by service providers, and can be used in conjunction with most end user email systems.
This whitepaper looks at a possible alternative to the BlackBerry email service constructed using open standards, and in particular using LEMONADE for email access. The focus of this paper is on protocol and architectural issues for mobile email. This paper starts by showing a comparative architecture of each system, and then provides a more detailed comparison.
BlackBerry Enterprise Service (BES)
The essential BES architecture is shown above. The BES server is operated by an enterprise, closely coupled to an Exchange or Notes server. The BlackBerry Client interacts directly with the BES server, to provide access to the various BlackBerry services.
An additional (optional) server is used to handle attachments, as illustrated above. When a message is sent from the Blackberry server system to a Blackberry Client, the core text message is sent to the BlackBerry client. If the message has attachments, they are removed and placed into an Attachment Server. The BlackBerry client can selectively preview and fully or partially retrieve attachments using the BlackBerry proprietary Universal Content Stream (UCS) protocol. This is a server side attachment handling approach, using a general purpose display mechanism to interact with the client.
The traditional BlackBerry client running on BlackBerry hardware uses UCS for all attachment display. BlackBerry client software is also available for other platforms, and the attachment handling varies. For example, the PocketPC version uses UCS for some attachments (e.g., Word, PDF) and behaves like a standard BlackBerry for these attachment types. Other attachment types (e.g., Excel) are handled by tools on the client, and behaviour for these attachments is more like the LEMONADE architecture.
BlackBerry Internet Service (BIS)
The BIS architecture initially looks identical to the BES one. The key difference is that BIS is less tightly coupled to the back end server, enabling support of a wide selection of email servers by BIS. BIS will poll the back end servers at intervals, typically 15 minutes. There is no separate attachment service, although similar functionality is available as a part of BIS, with UCS client access. Attachments are limited to 5 Mbytes, and there are additional mailbox size controls.
LEMONADE Architecture
The LEMONADE architecture has direct access from the client to the messaging server. Desktop and mobile clients use the same protocols to access the message server, and there is no intermediate service as with BlackBerry. A few details are useful to understand this architecture in comparison to BlackBerry:
- The client is alerted to new messages by the IMAP IDLE operation, and will generally then get summary information on new messages to present to the user. This is described in more detail in the Isode Whitepaper IMAP IDLE: The best approach for 'push' email.
- Messages are generally retrieved selectively under user control, including information on message structure and attachments.
- Attachments are downloaded (partially or fully) from the server under client control. There is no additional attachment server. Attachments are rendered from their native format on the client device.
Using LEMONADE Indirectly
LEMONADE is specified as a direct client/server architecture. It can be deployed in a two tier architecture as illustrated above. This is the model in which the Open Mobile Alliance (OMA) envisage deploying LEMONADE, as described in the Isode White Paper IETF and OMA architectures for mobile email.
An example realization of this architecture is achieved by Isode's Isode M-Box POP/IMAP Gateway product that provides support for LEMONADE Clients, synchronizing with other email servers at the back end using POP3, which is supported by most email servers.
Comparison of Email Capabilities
This section gives a side by side comparison of BlackBerry BIS, Blackberry BES and LEMONADE.
| Feature | Blackberry Internet Service (BIS) | Blackberry Enterprise Service (BES) | LEMONADE |
|---|---|---|---|
| General Architecture | Front end server that accesses consumer mail server. | Front end server closely coupled with Exchange or Notes. | Direct client access to mail server. |
| Open Standards | No | No | Yes. See Isode White Paper LEMONADE Profile: The Key Standard for Mobile Messaging |
| Support of general message send and receive capabilities | Yes | Yes | Yes |
| Secure Access (Authentication and Data Confidentiality) | Yes | Yes | Yes (SASL & TLS) |
| Push Email | Yes, but with delay due to back end polling (typically 15 minutes) | Yes | Yes. See Isode White Paper IMAP IDLE:
The best approach for 'push' email |
| Transfer of Text Emails | Yes (always) | Yes, as for BIS | Yes (under client control). Allows deletion, filing or forward of messages without download |
Notification of email address errors before submission is completed |
No. Address errors come back as separate messages up to 15 minutes later | Yes | Yes |
| Forward without Download | Yes (for complete messages with attachments) | Yes, as for BIS. | Yes (for all messages). Can also include selected attachments without download |
| Deletion of Messages on Server (Synchronization) | No. Messages need to be deleted separately on the BlackBerry Client
and the Server (or Desktop) |
Yes | Yes |
| Full and Partial retrieve of attachments. | Yes (5 MByte attachment size limit) | Yes | Yes |
| Linear attachment preview, retrieving only the parts of the document being previewed | Yes | Yes | Yes (provided that viewer can handle partial documents) |
| Non-linear preview, without full download | Yes. For example: single screen display of image; zoom into image; display powerpoint list of slides. | Yes, as for BIS. | No. Full document must be retrieved to get equivalent functionality. |
| Transfer of attachment from client (e.g., to a PC). | No | No | Yes |
| Attachment editing (e.g., for making inline comments on a HTML document) | No | No | Yes |
| Support of new attachments formats | By enhancement to BlackBerry Attachment Service. | Yes, as for BIS. | Two approaches possible:
1.Enhancement to email client. |
Message Filtering |
Yes, using filter on blackberry server. | Yes, as for BIS | Yes. This can be done using either a SIEVE filter on the server or using a filter on the LEMONADE client. See Isode Whitepaper BlackBerry and LEMONADE Approaches to Mail Filtering for more details. |
| Access to Message Folders on the Server | No | Yes | Yes |
| Message Filing | No | Yes | Yes |
| Vacation Notification | Yes, can be set on Client or Server. | Yes, as for BIS. | Yes, using SIEVE, which is typically managed with a Web interface. |
Analysis of LEMONADE vs BlackBerry BES
The protocol capabilities of Blackberry BES and LEMONADE are broadly similar, and there are no significant identified features which are missing or substantially superior in either protocol set. Both protocol sets have minor advantages over the other, when making a detailed analysis. The most significant difference that will be user visible is attachment handling.
Both approaches are quite viable and sensible for handling mobile email attachments. When the BlackBerry was introduced, client processing power would have been inadequate for a LEMONADE approach, and so the BlackBerry choice would have been the only viable option. Modern PDAs and Phones have plenty of processing capacity, as demonstrated by the availability of client software to render most popular attachment formats.
The non-linear preview capability in the BlackBerry architecture may be useful and cannot be done with the current version of LEMONADE. The benefits of having the attachments in native format on the client (as opposed to UCS) can also be significant, and this approach is likely to be preferable for most users.
BlackBerry BIS
LEMONADE and Blackberry BES both offer significant functional advantages over Blackberry BIS. The lack of synchronization of deletions, and lack of access to server folders would be highly undesirable for most moderate and heavy email users.
Putting together a Complete LEMONADE System
This document is comparing a deployed system with a protocol architecture. This is not a fair comparison, as it is easy for a theoretical system to be better. This section looks at each of the components of the BlackBerry solution (as listed at the start of this paper), and comments on availability for someone looking to build a LEMONADE deployment.
- Server Software: Available now. Isode R12.0 is the first available LEMONADE compliant server solution, including management tools. Products are anticipated from other vendors.
- Client/Server protocol: The topic of this paper.
- Client Hardware and associated OS: Good mobile hardware platforms and associated OS are widely available, and the focus of a number of companies.
- Client Software: Not yet available.
- Management Tools: These would generally be expected as part of the server software solution, and other tools as part of the Client Software management.
- Wireless network integration: Technology and skills for wireless network integration are widely available.
The quick summary of this analysis is that everything needed is available, except for client software. Although no fully LEMONADE compliant mobile client products are available, there are a number of IMAP/SMTP products that provide a substantial subset of the LEMONADE functionality. The functionality not available is essentially:
- Features that will enhance performance. The lack of these features will not usually be noticed by the end user.
- Forward without download.
These gaps are not large, and it is likely that they will be closed soon. In practice, a very effective solution could be deployed now. Products that Isode would recommend for the three major mobile platforms are:
- PocketPC/Windows Mobile Smartphone: Flexmail
- PalmOS: ChatterMail
- Symbian: Profimail
Address Books & Calendars
Certain functions are often closely associated with email, in particular Address Book and Calendaring, and to a less extent functions such as task lists and notes. These are not handled by LEMONADE, but support is clearly important for an overall integrated solution.
Personal Address Book and Calendars are best handled by a synchronization protocol. The OMA defined 'SyncML' protocol is ideal to achieve this.
Synchronization can be handled to the desktop or to the server. For most users, desktop synchronization is ideal. Email applications will generally be build over the native platform address book, so that common addressing is available for all applications. Most mobile devices provide excellent desktop synchronization capability, either using SyncML or proprietary mechanisms. Where server synchronization is required, there are a number of commercial and open source solutions.
More detailed discussion of this area is given in the Isode Whitepaper Access, Replication and Synchronization for Mobile Email Devices.
Further Functions & Third Party Applications
Mobile devices are becoming platforms to support a wide range of applications, not constrained to a single function. General support of non-email capabilities is beyond the scope of this paper.
One of the key attractions of using a general purpose OS platform such as PalmOS or PocketPC, is the wide range of third party applications available. Where application flexibility is required, it makes sense to choose a mobile device that is a platform rather than an appliance.
Conclusions
BlackBerry Enterprise Service and LEMONADE can be used to provide a similar level of service, and neither has any compelling advantage over the other. Both have substantial functional advantages over BlackBerry Internet Service. However, the use of Open Standards makes the case for using LEMONADE overwhelming, as set out in the Isode Whitepaper Open Standards: The best approach for Mobile Messaging.
