A Starlink user terminal attached to the roof of a building.SpaceXSpaceX is expanding the beta test of its Starlink satellite internet service, reaching out via email on Monday to people who expressed interest in signing up for the service.Known as the “Better Than Nothing Beta” test, according to multiple screenshots of the email seen by CNBC, initial Starlink service is priced at $99 a month – plus a $499 upfront cost to order the Starlink Kit. That kit includes a user terminal to connect to the satellites, a mounting tripod and a wifi router. There is also now a Starlink app listed by SpaceX on the Google Play and Apple iOS app stores.”As you can tell from the title, we are trying to lower your initial expectations,” the emails said, signed Starlink Team. “Expect to see data speeds vary from 50Mb/s to 150Mb/s and latency from 20ms to 40ms over the next several months as we enhance the Starlink system. There will also be brief periods of no connectivity at all.”The emails, sent to an unspecified number of users, marks the launch of SpaceX’s public beta test of the emerging internet service. For the last few months SpaceX has conducted a limited private beta test with employees – which the company has said showed strong results in both latency and download speeds, key measures for an internet service provider.SpaceX did not immediately respond to CNBC’s requests for comment.Those who received the emails would have filled out a form on the Starlink website, which asked for potential subscribers’ contact information and location. Elon Musk’s company posted that form in June and, less than two months later, SpaceX said that “nearly 700,000 individuals” across the United States had indicated interest in the service.Starlink is SpaceX’s plan to build an interconnected internet network with thousands of satellites, designed to deliver high-speed internet to anywhere on the planet. The network is an ambitious endeavor, which SpaceX has said will cost about $10 billion or more to build. But the company’s leadership estimate that Starlink could bring in as much as $30 billion a year, or more than 10 times the annual revenue of its rocket business.A Falcon rocket launches a Starlink mission in October 2020.SpaceXTo date, SpaceX has launched nearly 900 Starlink satellites – a fraction of the total needed for global coverage but enough to begin providing service in some areas, including in the northwest United States. The company has begun to work with a handful of organizations in rural regions which Starlink satellites in orbit currently cover, such as Washington state.”Under Starlink’s Better Than Nothing Beta program, initial service is targeted for the U.S. and Canada in 2020, rapidly expanding to near global coverage of the populated world by 2021,” SpaceX said in the description of its Starlink mobile app.SpaceX earlier this month announced a partnership with Microsoft, to connect the tech giant’s Azure cloud computing network to the Starlink network. SpaceX and Microsoft in recent months have been testing the software needed to connect Starlink and Azure. The partnership is especially key to Microsoft’s new mobile datacenters, which the company says are designed “for customers who need cloud computing capabilities in hybrid or challenging environments, including remote areas.”Subscribe to CNBC PRO for exclusive insights and analysis, and live business day programming from around the world.