X0306 4 2022-05-19 1 0001644675 Mimecast Ltd MIME 0001326427 Schwartz Hagi C/O MIMECAST NORTH AMERICA, INC. 191 SPRING STREET LEXINGTON MA 02421 1 0 0 0 Ordinary Shares 2022-05-19 4 D 0 10676 D 0 D Ordinary Shares 2022-05-19 4 D 0 26059 D 0 I By Schwartz Family Trust Restricted Share Units 2022-05-19 4 D 0 2742 D 0 D Pursuant to the terms of that certain Transaction Agreement between Magnesium Bidco Limited ("Magnesium Bidco") and Mimecast Limited ("Issuer"), dated December 7, 2021 (the "Transaction Agreement"), Magnesium Bidco agreed to acquire all of the issued and to be issued ordinary shares of Issuer for $80.00 per ordinary share by means of a court-sanctioned scheme of arrangement (the "Scheme"). At the effective time of the Scheme on May 19, 2022 (the "Effective Time"), each ordinary share then outstanding was automatically transferred from Issuer's shareholders to Magnesium Bidco in accordance with the Scheme and the Transaction Agreement, and Issuer's shareholders ceased to have any rights with respect to the Issuer ordinary shares, except their rights under the Scheme, including their right to receive $80.00 per ordinary share, subject to required withholding taxes. These shares are held by the Schwartz Family Trust (the "Trust"). The Reporting Person is a beneficiary of the shares held by the Trust and is the sole trustee of the Trust. Each restricted share unit ("RSU") represents a contingent right to receive one Issuer ordinary share. At the Effective Time, each RSU that was vested and outstanding as of immediately prior to the Effective Time ("Vested RSU") was canceled and converted into the right to receive an amount in cash equal to $80.00 multiplied by the aggregate number of shares subject to such Vested RSU, subject to required withholding taxes. These RSUs were granted on October 6, 2021 and vest in full on the one year anniversary of the date of grant. /s/ Robert P. Nault, Attorney-in-Fact 2022-05-23