In this age of unrelenting spam, it's hard to imagine the work required to secure 64,000 inboxes from viruses, phishing scams, unwanted solicitations and other email threats.

Renate Tomesch, global enterprise messaging manager at automotive, battery and building-component manufacturer Johnson Controls of Milwaukee, doesn't have to. She outsources it.

Despite the popular belief that technology services are most often used by small- and mid-sized businesses, since large enterprises have the staff and resources to perform these tasks in-house, Tomesch made the decision two years ago to go with a hosted email security provider.

"Because Johnson Controls is also in the business of outsourcing - we handle other companies' building maintenance - I know if something isn't native to your business, outsource it if it's feasible," says Tomesch.

That decision was made after the email security appliances Johnson Controls had in house buckled under the heavy load of spam that dominated the company's inbound mail stream. "With servers we normally assume a three-year life. After two years with these appliances we realised they weren't doing their job anymore," she says, adding that not only were the appliances letting more spam through than was acceptable, but they were also slowing down the flow of email.

The company evaluated two other appliance vendors and two managed service companies, and decided to go with Postini's email security offering. Tomesch did an analysis and figured the cost difference of outsourcing email security vs. performing the task in-house was not great enough to factor in, and with the outsourced service she wouldn't again be put in the position of having her infrastructure pass its capacity limits.

"Maybe we were a little visionary in saying that with a managed solution, we never again would have to concern ourselves with the growth of spam," she says. Particularly since spam has grown significantly over the past year, and shows no signs of letting up, "I look back and say, `Oh am I glad I made that choice.'"

Johnson Controls hasn't gone with outsourcers across the board; the company manages its own Lotus Notes email system and doesn't use some of Postini's other offerings such as email archiving, Web filtering or instant-messaging security. And there's still the task of managing the relationship with Postini, such as letting the company know when its service missed spam messages. As a premium customer, Tomesch's team meets with Postini every month to discuss what's working with the service and where there's room for improvement.

But considering that Johnson Controls receives between 3.5 million and 4 million emails per day and only 250,000 are valid messages, Tomesch is happy to let Postini do the heavy lifting.

"We rely on them to do whatever it takes to keep as much spam away from us as possible," she says.