Windstream acquired the business in its merger with EarthLink in February 2017.
Trive Capital, a Dallas-based private equity firm, purchased the business for $330 million in cash.
"This transaction enables us to divest a non-core segment and focus exclusively on our two largest business units. In addition, it improves our credit profile and metrics in 2019 and beyond," said Tony Thomas, president and CEO of Windstream.
EarthLink offers Internet access, online backup, managed web design, web hosting and various email services to more than 600,000 customers throughout the United States.
"We are excited to partner with and support the EarthLink management team in continuing to provide great products and services available to millions of households in the United States," commented Trive Managing Partner Conner Searcy. "We intend to provide additional resources and access to deep industry relationships to help grow the brand in the coming years."
Earlier in December, Windstream sold certain fiber assets in Minnesota to Arvig Enterprises, a Minnesota-based provider of telecommunications and broadband services. The all-cash transaction was valued at $49.5 million.
Windstream also entered into a definitive agreement to sell additional fiber assets in Nebraska to Arvig for $11 million. The Nebraska sale is expected to close in the first quarter of 2019.
As part of the transactions, Windstream will establish a fiber network relationship with Arvig, allowing Windstream to utilize the assets to continue to sell its products and services in Minnesota and Nebraska.