X0306 4 2021-12-01 0 0001644675 Mimecast Ltd MIME 0001863284 Leger Bernd C/O MIMECAST NORTH AMERICA, INC. 191 SPRING STREET LEXINGTON MA 02421 0 1 0 0 Chief Marketing Officer Restricted Share Units 2021-12-01 4 A 0 5239 0.00 A 5239 D Restricted Share Units 28021 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 December 1, 2021. Twenty-five percent (25%) of the units vest on December 1, 2022 and the remainder of the units vest on an annual basis over the next three (3) years, provided that the Reporting Person remains an employee of the Issuer on each such vesting date. These restricted share units were granted on June 1, 2021. Twenty-five percent (25%) of the units vest on June 1, 2022 and the remainder of the units vest on an annual basis over the next three (3) years, provided that the Reporting Person remains an employee of the Issuer on each 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 May 24, 2021). /s/ Robert P. Nault, Attorney-in-Fact 2021-12-02