Mimecast Limited received a higher takeover offer during its go-shop period but rejected the bid on antitrust grounds, according to people familiar with the matter. Proofpoint Inc. offered on December 31, 2021 to buy Mimecast for $92.50 per share in cash, said the people, who asked to not be identified because the matter isn't public. While that's higher than Permira's cash bid of $80 per share, Mimecast rejected the offer and Proofpoint's request to conduct due diligence because it viewed the bid as carrying too much antitrust risk, they said.

The special committee Mimecast set up to review the offer had concerns that the combination would involve a drawn-out review process, with a good chance of failure, the people said. Mimecast met with Proofpoint several times and Proofpoint couldn't reassure Mimecast on those concerns, they added. It's unclear whether Proofpoint, which had indicated it could raise its offer pending due diligence, will keep pursuing Mimecast.

“On December 31, 2021, portfolio company A submitted to the special committee a non-binding expression of interest to acquire all outstanding ordinary shares of Mimecast at a price of $92.50 per share in cash,” Mimecast revealed in a filing January 13, 2022. The revelation of Proofpoint's interest could make it harder for Mimecast to secure shareholder approval for the Permira deal. A representative for Mimecast declined to comment.

Representatives for Sunnyvale, California-based Proofpoint and Thoma Bravo couldn't immediately be reached for comment.