Rackspace today announced that they are acquiring Webmail.us, a well-known provider of email hosting services. The purchase price of the deal was not disclosed, but Webmail reportedly has around $6M in annual revenues. That’s not a lot compared to Rackspace, but when you consider that Rackspace now has a new hosted offering to sell to it’s growing customer base, it could leverage the acquisition into some serious profits.

This is a growing market, considering that computer users are growing tired of Microsoft’s bloated Office release every 5 years. It has prompted companies like Google to launch their Google Apps, and newcomers like Zoho to launch an entire online suite of Office-like products.

Rackspace has been sending IPO signals to the market recently by announcing quarterly revenues. It’s a very wise move to get some acquisitions done now before there is tighter public scrutiny.