On Monday, Amazon (AMZN) announced the general availability of WorkMail, the company’s cloud-based email and calendar platform, with the addition of several new features.

The platform, which was first announced one year ago, is being marketed as Amazon’s alternative to similar email and collaboration offerings such as Microsoft Exchange and Google Apps, but with a tighter focus on security.

WorkMail does not provide all of the features of Google and Microsoft’s cloud-based apps — there’s no word processor, for example — but it competes in the most important categories. It also offers some traits not available from other services, like a dead-simple way to host email on a custom domain name.

And, unsurprisingly, WorkMail features easy integration with other Amazon cloud products.

On Monday Amazon announced that WorkMail, which had been available only in preview mode, is now in general availability. The company has also upgraded the platform’s feature set in several key areas.

On the security and compliance front, WorkMail now features the ability to keep data in a specified geographic region. It also offers new ISO certifications.

Client support has been extended, too, with added compatibility for email clients on Mac OS X and several mobile platforms.

And perhaps most importantly, Amazon has added a migration tool that will help organizations convert from Microsoft Exchange to WorkMail. That lowers the entry barrier to almost nothing for organizations that currently have on-premise solutions.

Price-wise, WorkMail is on a par with Gmail and Office 365. That means that organizations that have already invested in those Web-based solutions might not yet find a compelling reason to switch. But for those still maintaining email and calendar suites in-house, WorkMail’s managed platform could prove an attractive alternative.