At the most basic level, enterprise antispam systems protect organizations against e-mail-related threats by identifying and removing junk mail and malicious messages. Some of the major threats, according to Radicati Group, include viruses, directory harvest attacks and denial of service attacks.

These systems have also broadened their approach to keep up with increased compliance needs and the evolution of e-mail threats toward phishing and malware-distribution URLs, according to Chenxi Wang, an analyst at Forrester Research. For instance, many systems now support antivirus, content filtering for inbound and outbound e-mail as well as Web and instant messaging traffic, encryption, archiving and e-discovery, or they integrate with systems that offer these functions, she says. Forrester calls this type of system "e-mail filtering"; Radicati, "e-mail security"; and Gartner, "e-mail gateway."

Also see Spam Management Best Practices

Antispam systems come in three forms: software, appliance and hosted service. While software is currently the largest segment, according to Radicati, appliances make up the fastest-growing category, with a 50 percent annual growth rate over the next four years. The second fastest-growing category is hosted solutions, Radicati says.

Buyers increasingly want a turnkey solution for e-mail filtering, Wang says, which explains the popularity of appliances and­, increasingly, hosted services, as they both decrease costs and simplify management. Leading appliance vendors, according to Forrester, are Cisco Systems, Symantec and McAfee/Secure Computing. Leading service vendors are Google/Postini, Microsoft, Symantec/Message Labs and Websense. Gartner expects to see more hybrid solutions emerging, which include an on-premises appliance and a hosted service with a single management interface and the ability to seamlessly migrate functions from one to the other.

Antispam Market Overview

According to Radicati, revenue for all three segments of antispam is forecast to grow from slightly over $3.9 billion in 2008 to over $6.2 billion in 2012.

Organizations are spurred to protect themselves against e-mail threats because of the costs associated with managing spam, loss of user productivity, network downtime, bandwidth costs, compliance and privacy concerns. Since many companies already have antispam systems installed, a significant portion of this market's growth can be attributed to upgrade and replacement, Radicati says.

Core Functionality

When Forrester evaluated e-mail filtering vendors in a recent study, it included vendors that offered the following capabilities:

* Antispam, antivirus and content filtering for both inbound and outbound e-mail traffic.

* Support for common compliance policies, such as HIPAA, PCI DSS, Sox and the Gramm-Leach-Bliley Act.

* Filtering capabilities beyond e-mail, either in Web or instant messaging.

Nine tips for choosing an antispam solution

DO go beyond antispam functionality. With spam accounting for 80 percent to 90 percent of all e-mail today, it's become essential to have an antispam system, Gartner analyst Peter Firstbrook says, and all current systems can be counted on to block almost 100 percent of spam. But if you're buying an antispam system today, make sure it goes beyond that to include more holistic functionality for e-mail protection, such as data loss prevention (DLP) and encryption. "Even if you're not going to use it right now, you will in the next three or four years," he says. "You want to buy a platform that allows you to expand to that without reinvesting in another down the road."