One of the few controls that mail administrators have at their disposal to curb the ever-increasing email volume traversing their networks is the maximum message size limit. Most companies deploy one size limit for their internal network and another for messages send to the Internet. At first glance, the reason for imposing size limits seems obvious enough. Who would want their mail server and network to come to a crawl or worse crash because a careless employee had sent a 600MB wmv file via email of junior taking his first steps. Naturally, most firms have put draconian restrictions in place, in many cases somewhere around 5-10MB for external and 10-20MB for internal messages.

One would think that these restrictions are reasonable and not an issue, but wait until your top sales executive is unable to deliver a RFP response to a potential client via email before the submission deadline. She doesn’t care why her heavily illustrated word document of over 10MB got caught by the outbound size limit, she just wants the email delivered.

Here are the three most common problems related to message size limits:

• Many companies do not tell their employees about the limits they put in place, their exact size and purpose.
• The method for choosing an allowable maximum message size is often completely arbitrary.
• Message size limits are typically imposed indiscriminately with a “one-size-fits-all” approach across the entire company.

As a result, users will resend rejected emails multiple times, waste time by calling the helpdesk and get frustrated. The “smarter” ones might even circumvent the system by packaging the large attachments into smaller chunks that are then sent in multiple messages or worse use a personal email account on a public service with lesser restrictions.

What many email administrators don’t realize is that their size limits are missing the mark.

The chart above illustrates the typical message size distribution and the resulting volume impact on the network found in literally all corporate email environments. It vividly shows that messages between 0.5- 5MB in size, sent repeatedly and to many recipients at a time are the real burden on the infrastructure (75% of the total data volume is caused by messages <5MB). The ripple effect of a 2MB PowerPoint sent to 50 or more people distributed throughout the network is far greater than the impact of a single large message.

Our consultants refer to this chart tongue-in-cheek as the “finger –chart”…

There are solutions to this dilemma:

• Conduct an email audit to better understand the typical message traffic patterns in the environment. The results should be broken down not only by mail topology, but also by geography, departments and even employee role or title.
• Set reasonable maximum limits on the outbound gateways that allow users to conduct their typical business with some room for exceptions. Enable multiple outbound queues on the gateways to avoid delivery delays due to single large messages.
• Enable smart message size handling on the internal servers. A dynamic enforcement solution that calculates the resulting net impact of individual emails combined with a flexible rules-based workflow will curb the true abusers and allow raising overall limits while lowering infrastructure costs.

Make sure to consult with the business users: Present the findings of the audit, request input and inform them of any resulting policy adjustments before implementing any wide-ranging changes. That effort combined with ongoing monitoring and reporting will certainly improve user satisfaction and ultimately make an admin’s job easier.

Technorati Tags: message size limit, email management, email enforcement, email monitoring

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