Mailgun, an email API delivery service, announced today that it was selling a majority stake in the company to private equity firm Thoma Bravo. The companies did not share terms, but this is the second owner in the company’s eight-year history.

Mailgun provides API services for building email functionality into applications. It has more than 150,000 customers using its APIs, according to data provided by the company.

In a blog post announcing the investment, CEO William Conway said the new money should help the company expand its capabilities and accelerate the product roadmap, a common refrain from companies about to be acquired.

“We will be investing millions in the development of products you can use to enhance your deliverability, gain more insights into your emails and deliver an unparalleled experience for your customers. We’re also doubling down on customer success and enablement to ensure our customers have exactly what they need to scale their communications,” Conway wrote in the blog post.

The company, which was founded in 2010 and was a part of the Y Combinator Winter 2011 cohort, has had a complex history. Rackspace acquired it in 2012 and held onto it until 2017, when it spun out into a private company. At that point, Turn/River, another private equity firm, invested $50 million in the company. After today’s deal, Turn/River will maintain a minority ownership stake in Mailgun.

Mailgun typically competes with companies like Mailchimp and SendGrid. Thoma Bravo has a history of buying enterprise software companies. Most recently, it bought a majority stake in enterprise software company Apttus. It also has investments in SolarWinds, SailPoint and Blue Point Systems.

Thoma Bravo did not respond to a request for comment before publishing.