By Bob Martin, Software.com

Driven by their increasing dependence on e-mail as a means of daily communication, users expect e-mail to be ever more reliable and accessible. This is true regardless of whether they use e-mail in the context of a corporate system, in conjunction with an online service, or as part of an Internet-access subscription. In order to meet these galloping expectations, organizations that evaluate and deploy messaging solutions -- both corporate IT departments and Internet Service Providers (ISPs) -- must rethink their criteria, whether they're supporting five users, five hundred thousand or more.
To achieve levels of performance that will create user confidence in mail systems, these organizations must first commit to delivering "dial-tone-quality" service. This focus on telephone-like levels of quality will necessarily transform the way they evaluate messaging systems. New features, which have often been a primary selection criterion, now become secondary. In their place is the messaging infrastructure's ability to deliver performance that meets the needs of the user population, bearing in mind that those needs are constantly evolving. For example, users are now sending larger, more frequent messages, while increasingly demanding remote access. It's this incredible and often unanticipated growth that is pushing the fundamental shift in evaluation criteria.
Crucial aspects of "dial-tone-quality" messaging include guaranteed scalability, reliability, and availability. When these criteria are at the forefront of an evaluation, the result is a messaging solution that services current and future user bases, handles message traffic with ease, transcends geographical issues, and extends to support a variety of integrated messaging applications. Here are some of the issues to consider within each category.

Scalability
Graceful scaling of a messaging system ensures its ability to handle increased message capacity and new users without a misstep. Scalability needs to be evaluated on multiple dimensions, depending on the volume of traffic and the number of users supported. A dial-tone system needs to scale vertically (e.g., adding more capacity to existing servers, as well as horizontally, which is accomplished by adding servers to increase capacity). Beyond the dimension of simple scalability are quality of scale issues: Will any service capacity expansion be transparent to users? When hardware is added to increase performance, does it benefit existing users, or only new ones? Does the mail system have a fully distributed design? Can different parts of the system be situated in different geographic locations? Can the system load be transparently balanced among multiple servers?

Reliability
Reliability focuses most on exception handling and "what if's…" and is a key aspect of dial-tone quality. Are messages lost if a server crashes? Are messages written to disk before a server accepts responsibility for them? What happens if a message is half written when the hardware crashes? Is the inter-server communication protocol transaction-based? Is the system tolerant of Internet outages? Is backlogged mail for remote sites stored together or is it separated by domain?

Availability
Central to successfully delivering the availability are the following: Are the mail server components "high-availability" (HA) aware? Do the mail server components include a "heartbeat monitor?" How is continuous availability provided -- server redundancy, server failover, or a combination of both? Which components are designed to be highly available -- Message Transfer Agent (MTA), MS, Post Office Protocol (POP), Internet Message Access Protocol (IMAP), Directory?

Native Internet Mail
In addition to the other criteria, organizations should strongly embrace native Internet mail to their list of criteria for "dial-tone-quality" messaging systems. Native Internet messaging support, without use of gateways or connectors to convert proprietary protocols or message formats, ensures message fidelity while eliminating numerous complexities from the mail equation. The result is simplified processes for communicating across organizations and groups, and in the public domain. In one of the best examples of a native Internet mail system, there are upwards of 35,000 users sending a million or more messages per day, with the entire system running on six servers. That system delivers the scalability and reliability that an organization of that size demands -- by virtue of embracing native Internet mail protocols.

Additional Considerations
While not directly related to the issue of "dial-tone quality," when considering messaging alternatives, it's advantageous to include Integrated Messaging capabilities -- fax and voice-mail integration -- for either current or future applications. The ability of a system extend and expand to include these services, either natively or via partner products, while maintaining dial-tone quality, enhances the long-term value proposition that a system offers.
While dial-tone-quality e-mail is a lofty goal, it's one worth pursuing and demanding. The hurtles are far from insurmountable and the rewards -- both to the user communities being served and on the administration side -- are well worth the effort.

Bob Martin will be speaking on the "Tens of Thousands of Messages Per Day" session on Wednesday, April 29 from 4:30-6:00 at EMA'98 in Anaheim, California.