Officially launched on Monday, Concentric's Perimeter Email Security service provides small to medium-sized businesses with a variety of email security that can drastically reduce server load, and prolong the life of an in-house email solution.

"We're going to allow customers, with our perimeter email protection service, to hide business mail servers behind our perimeter," says Nate Gilmore, director of marketing at Concentric. "And we will handle all of their DNS denial of service issues and dictionary harvest attacks on the DNS side. We're going to help them with initial user validation so that they can cut front end mail server load by making sure that dictionary harvest attacks can't hit the email server."

In addition to the regular helping of spam and virus mail, says Gilmore, an unprotected mail server can be regularly flooded with requests from spammers conducting dictionary harvest attacks. The attack will bombard a server with countless computations of letters, determining from the combinations that don't bounce back which are legitimate accounts.

"A dictionary harvest attack is an incredible amount of load on a server," says Gilmore. "We offer a service, and we include it bundled - I won't say free, because they have to have the base level account - and you hide your server behind our perimeter. You upload your user list. And then we'll take the front-end brunt of those attacks."

Unverified mail hitting the Concentric perimeter reduces server load dramatically, with only mail to verified addresses getting through. Incorrectly addressed mail is dropped without bouncing back, protecting the legitimate addresses from being harvested.

After the basic perimeter is applied, users can buy additional services. User validation for up to 80 accounts is included with the basic Concentric bundle, a package that includes a shared Web hosting account.

"For $15 a month you upload 80 users and we'll protect those 80 users against dictionary harvest attacks and then we'll also give your mail server kind of a disaster recovery model to it," says Gilmore. "If the mail server goes down, we'll continue to spool mail. And then we'll send it all to your mail server once the mail server comes back up."

On top of the basic PEP protection, the company offers spam and virus filtering for $1 per user per month. And beyond basic filtering, Concentric offers enhanced filtering for what Gilmore calls "power users," those email accounts, often a PR or marketing contact with a published address, that have particularly pronounced spam profiles. For another $1 per user per month, a power user can install Premium Junk Mail Filtering, a tool that can be quickly trained to operate with close to 100 percent effectiveness.

"So if we had an 80-person company," says Gilmore, "how much would it cost them to get all this? Let's say $15 a month for the base level account, $80 a month if they turn on spam and virus filtering for all 80 users. And let's say 10 percent of their users are power users. That's $103 per month. And for that $103 per month, they're ensuring that their mail server is essentially only receiving legitimate mail."

Gilmore says the service is particularly targeted to certain existing customers of its services - customers of its managed DNS services or access and hosting bundles. He says the customers that have already deployed the service have been very happy with the results.

"Their mail servers are no longer being overwhelmed. They're no longer having to augment them with additional mail servers they have to pay software licensing fees for. And they don't need to staff up, and add more and more services to correct it. But they still get to maintain that mail server and extend the life cycle."