"ACI looks equally as attractive when you compare its current revenue multiple to recent transaction comps," Smith, Starboard's chief executive officer and chief investment officer, said.

Smith told the Capitalize for Kids Virtual Investors Conference that the company has underperformed peers including Blackbaud, Commvault Systems, and FireEye among others, despite its favorable business characteristics and unique collection of assets.

Over the past five years ACI has returned 37%, much less than the 151% gain of its peer group, Smith said, according to the firm's presentation which was obtained by Reuters.

Smith noted an "unprecedented amount of M&A activity in the payments space in recent years," noting that both strategic and private equity buyers have been active. "The valuations paid for recent acquisitions exceeds the multiple that ACI is currently trading at," he said.

ACI's stock price closed at $31.55 on Thursday, roughly where it closed on Monday before Starboard said it now owns 10.5 million shares in the Naples, Florida-headquartered company which is worth $3.7 billion. The company did not comment on Smith's presentation.

Starboard, which invests roughly $6 billion, is known for its operational know how and improving public companies like Darden Restaurants. Starboard has already won 22 board seats in 2020, including three at data management software maker Commvault Systems, an ACI peer.

Starboard said there is room for ACI to speed up organic growth with expanding operating margins and said that new management is taking sensible steps. But Smith and his team also want to hear details at the upcoming investor day and understand whether all units are core to the company.

(Reporting by Svea Herbst-Bayliss; Editing by David Gregorio)

By Svea Herbst-Bayliss