 SAN DIEGO, April 26, 2021 PRNewswire -- Shareholder rights law firm Johnson Fistel, LLP has launched an investigation into whether the board members of Proofpoint, Inc. NASDAQ: PFPT Proofpoint, Inc. or the Company breached their fiduciary duties in connection with the proposed sale of the Company to Thoma Bravo. On April 26, 2021, Proofpoint, Inc. announced that it had entered into a definitive merger agreement with Thoma Bravo. 