The round also included several high-profile software entrepreneurs, such as Slack CEO Stewart Butterfield, the co-founders of digital payments upstart Stripe Patrick and John Collison, and Jason Fried, co-founder and CEO of Basecamp, a fast-growing project management startup.

The new money brings Intercom’s total backing to $116 million. The startup’s co-founder and CEO, Eoghan McCabe, declined to discuss the valuation, but he noted the company won’t need more funds. The new money will be used for product development. Intercom already devotes 85% of its “tens of millions” of dollars in revenue to research and engineering.

It’s hard to pigeon-hole Intercom’s software into one software category. Broadly speaking, it handles “customer communications,” including help desk support interactions as well as marketing activities. As a result, it competes with a wide range of incumbent software companies ranging from customer support specialists, like Zendesk, as well as marketing automation players that have traditionally specialized in smaller companies, such as Marketo or Mailchimp.

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The company has added more than 3,000 paying customers since the first part of this funding round in August 2015, bringing the total count to 10,000, McCabe cited.

“Unlike conventional software companies, the strength of our technology has generated incredible organic revenue growth, meaning we don’t have to pump a lot of capital into sales and marketing,” says McCabe.

Aside from Index and the individual investors already mentioned, Intercom’s latest infusion included previous investors ICONIQ Capital Bessemer Venture Partners and the Social + Capital Partnership.

The five-year-old company’s headcount currently stands at about 250 employees, split between Dublin and San Francisco.