Yes, Amazon is best known as an e-commerce company. But with its pioneering collection of cloud computing services, it's also an IT company, a company that serves up tech to the world's businesses. And its IT ambitions just keep getting bigger.

Today, the company announced an online email and digital calendar service dubbed WorkMail. According to the Wall Street Journal, WorkMail is meant to compete with email services from the likes of Microsoft. Amazon will charge $4 per month for each inbox, and workers can use it via Microsoft Outlook or other familiar email clients.

For added security, the WSJ reports, Amazon will provide technology needed to encrypt messages on WorkMail, while companies that use the service will control the keys needed to unscramble the encryption. Within certain industries and in countries where privacy is paramount—Germany and other European countries, for instance—Amazon will also provide a tool meant to ensure that emails are only stored in designated geographic regions.

With the new service, Amazon is joining a host of others in the quest to upend Microsoft as the king of email and other office productivity tools. Competitors include Google, with its Apps for Business, as well as myriad startups, including Dropbox, Evernote, Box.com, and Quip.