AlphaMail Is Scalable and Accessible Web Mail

AlphaMail takes a unique approach to providing a Web-based IMAP client.

AlphaMail is a high-performance, feature-rich, open-source Web mail system created at the University of Oregon. The interface includes message snippets in indexes, UTF8 composition and numerous viewers for attachments (such as image icon preview and file listings from tarballs). It also tries to strike a balance between desirable features and too much interface noise. It was created to address several problems that exist with other open-source and commercial Web mail systems.

Performance

The first concern AlphaMail addresses is performance. Almost all Web mail systems (such as Horde's IMP Web mail Client and SquirrelMail) use IMAP from within the Web server, which is incapable of persisting an IMAP session.

The IMAP protocol is designed to optimize access through persistent access, so this is an inherent and recognized problem. The problem is usually mitigated with an IMAP proxy that maintains a persistent connection. The problems with this solution are multifaceted.

One problem is that the code in the Web mail client itself cannot depend on the state of the IMAP connection and must repeat commands as if each mouse click were a new IMAP session. This is a problem, because the sequence of required events for a new session in the IMAP protocol include authenticating and selecting the desired folder. The benchmarks of several IMAP servers indicate that the repetition of the folder selection command, even if the folder is already authenticated and selected (that is, through a proxy), can cause significant extra server load.

These inefficiencies could be addressed through improvements in the IMAP server and proxy algorithms, but another problem is intractable: a proxy cannot improve the protocol. The fact that the Web mail client is using IMAP forces it to behave as a complete standalone client. If the developers want to add a complex feature, such as conversation views (à la Google mail), which requires complex message cross-referencing across several folders, the protocol itself becomes a major impediment.

AlphaMail solves these problems by including a middleware layer that uses a simplified and extensible protocol for the Web application and is responsible for optimizing access to the mail servers. The protocol supports highly specialized commands that allow the Web code to ask for the information needed for a page directly, without having to make any assumptions about the state of the IMAP connection.

This has the additional advantage that the IMAP protocol handling in the middleware layer can be written in a high-performance language (in this case C++), can cache results and can optimize the interaction. The middleware program is known as the imap_webcache, because it caches both data and network connections for the mail interaction.

Accessibility

The next concern was accessibility. Information systems in higher education, government and many other environments must support access for everyone. AlphaMail still is actively being tuned for access by the disabled, but it is already optimized for other access concerns. For example, site security policies might require or recommend that members of the community disable browser features that regularly appear in US-CERT advisories, such as JavaScript. The only Web e-mail I could find that did not require JavaScript for even basic functionality was SquirrelMail, and it was deemed too risky from a performance standpoint.

AlphaMail includes JavaScript enhancements, but those enhancements have traditional CGI alternatives that become active if JavaScript is disabled on the browser. All critical functions of the system will work with any browser, independent of capabilities and settings.

Installation

AlphaMail supports GNU autoconf and has been built cleanly on many Linux variants, FreeBSD, Solaris and Darwin (OS X). The easiest platform to install is Fedora Core 5 via yum(1), as described on the AlphaMail home page.

I highly recommend using Fedora Core 5 on a test machine to avoid the headaches of dependency resolution for your initial trial run. The actual build is pretty much what you'd expect, but solving runtime dependencies can be challenging.

If you decide on a source build, first you need to install the Boost C++ libraries (see Resources).

Installing Boost

You need the Boost Jam utility (usually named bjam) as well as version 1.33 or better of the Boost C++ libraries. Jam is sort of a combination between GNU autoconf and make. Follow the instructions from the Boost Web site for details, but essentially, extract the files and run:

# bjam install

In rare circumstances, you may want to pass options (such as an installation prefix). See the Getting Started guide on the Boost Web site if you have special needs.

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