X0306 4 2021-10-06 0 0001644675 Mimecast Ltd MIME 0001211069 SCHECHTER ROBERT C/O MIMECAST NORTH AMERICA, INC. 191 SPRING STREET LEXINGTON MA 02421 1 0 0 0 Restricted Share Units 2021-10-06 4 A 0 2742 0.00 A 2742 D Ordinary Shares 11692 D Restricted Share Units 2022 D Each restricted share unit represents a contingent right to receive one share of the Issuer's ordinary shares. These restricted share units were granted on October 6, 2021 and vest in full on the one year anniversary of the date of grant, provided that the Reporting Person remains a director of the Issuer on such vesting date. These restricted share units were granted on January 2, 2019, and 2,021 units vested on January 2, 2020, 2,021 units vested on January 2, 2021, and 2,022 units vest on January 2, 2022, provided that the Reporting Person remains a director of the Issuer on such vesting date. Exhibit 24 Power of Attorney (incorporated by reference to Power of Attorney filed as Exhibit 24 to Form 3 filed by the Reporting Person on January 2, 2019). /s/ Robert P. Nault, Attorney-in-Fact 2021-10-08