Security vendor Internet Security Systems this week plans to announce its foray into the packed e-mail security market with an appliance that does double duty: blocking spam and viruses while also preventing intrusion.

The Proventia Network Mail Security System will be available this month. It's designed to sit at an enterprise's gateway to block malicious e-mails from coming in and keep sensitive information from getting out, says Dave Ostrouski, senior manager of product marketing at ISS.

Despite the unique twist of adding IPS to spam and virus protection, ISS enters the e-mail security arena at a time when the overcrowded market is starting to mature and shake out, and companies have likely already placed their bets on the vendors they believe will survive.

ISS will go up against appliance makers Barracuda, CipherTrust, IronPort, Mirapoint, Proofpoint and others. The company asserts that because it offers products in other security areas - unlike many of its new competitors - organizations will want to standardize on ISS.

The Proventia Network Mail appliance blocks spam, viruses, worms, phishing attacks and other malicious code attempting to enter an organization through the inbound mail stream. It includes ISS' existing Virus Prevention System, which examines the behavior of network traffic to detect viruses before signature matches are released for them, Ostrouski says. The company also offers Sophos' antivirus technology as an add-on module.

Proventia Network Mail applies keyword matching to outbound e-mail messages so companies can ensure employees aren't sending out information protected by regulation or corporate policy, Ostrouski says.

The Proventia Network Mail Security System appliance, with integrated IPS, costs $20,300 and can support as many as 2,500 users.