X0306 4 2019-04-01 0 0001644675 Mimecast Ltd MIME 0001588892 Brown Rafeal E. C/O MIMECAST NORTH AMERICA, INC. 191 SPRING STREET LEXINGTON MA 02421 0 1 0 0 Chief Financial Officer Restricted Share Units 2019-04-01 4 A 0 50000 0.00 A 50000 D Share Option (Right to Buy) 47.23 2019-04-01 4 A 0 180000 0.00 A 2029-04-01 Ordinary Shares 180000 180000 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 April 1, 2019. Twenty-five percent (25%) of the units vest on April 1, 2020 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 such vesting date. This option was granted on April 1, 2019. Twenty-five percent (25%) of the shares vest on April 1, 2020, and the remainder of the shares vest on a quarterly basis over the next three (3) years, provided that the Reporting Person remains an employee 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 March 18, 2019). /s/ Robert P. Nault, Attorney-in-Fact 2019-04-03