Messaging lies at the heart of a business’ ability to communicate, to interact quickly and effectively with everyone from employees and suppliers to clients and prospects.

Yet supporting an on premise messaging solution absorbs much of a business’ IT dollars. In addition to buying the software, you must expend resources on maintenance, implementation, upgrades, licensing, support and archiving. Downtime – whether scheduled or due to failure or disaster – costs money, disrupts business operations and creates customer dissatisfaction, especially in a world where the vast majority of users check their emails from home, from on the road and after-hours.

Although many decision-makers claim on premise Exchange implementations are less expensive to deploy and operate than hosted Exchange, the opposite is often true. Just add up the dollars: A 10-person on premise Exchange solution costs $389.78 vs. $27.00 per seat per month for a hosted Exchange solution, for a total whopping savings of $362.78 or 93 percent, according to Osterman Research. At 100 users, on premise costs $37.29 per seat each month compared with a hosted service’s cost of $12.25 for savings of $25.04 or 67 percent. With 1,000 users, on-site costs $20.72 for each seat every month vs. $9.85 for hosted for savings of $10.87 or 52 percent, Osterman Research finds.

It is not surprising then that even some large enterprises are migrating to hosted Exchange: GlaxoSmithKline, for example, is moving its 100,000 users to hosted Exchange, the giant pharmaceutical company said in March 2009.

There are other savings, too. Because the cost-per-seat is fixed over the contract’s lifetime, your business has a predictable monthly outlay without the risk of unforeseen expenditures. If you support Exchange internally, you must take into account potential disruptive forces such as natural disasters, power outages and office relocations that can add unforeseen costs to your on premise Exchange management budget.

As you add employees, you run the risk of maxing out your internal infrastructure, forcing you to expend dollars and hours buying and installing servers, storage and other infrastructure to support new hires. Of course, this adds more costs to your existing Exchange budget at a time when you would rather spend IT funds on using technology to solve business challenges.