Microsoft said late Tuesday that its Custom Domains service had officially launched, making it the third Windows Live project to come out of beta. The service allows a customer to use a custom domain name with Windows Live Mail and Hotmail.

Windows Live Custom Domains is a free service, just like other Live offerings from the company. Additionally, with the final debut, Microsoft has launched a new feature called "open membership."

This would enable someone who owns a domain to allow users to sign up for an e-mail account without prior authorization from the administrator. The accounts would be available through Windows Live Mail and Hotmail, Microsoft said.

To promote this new feature, Microsoft has teamed up with the city of Waterloo, Beligum. Through Windows Live Custom Domains, the city will offer "@waterloo.eu" e-mail addresses to its 30,000 citizens. "We're honored to partner with Waterloo to offer this new technology to their citizens," the company said.

Microsoft isn't the only company trying to bring organizations onto its hosted mail platform. Google offers a similar free service for its Gmail users called Gmail for Domains.

More Windows Live services are expected to come out of beta through the rest of the summer. Microsoft has said over 20 new services are currently planned for the Live platform.