X0306 4 2020-10-01 0 0001644675 Mimecast Ltd MIME 0001825341 Paisley Michael C/O MIMECAST NORTH AMERICA, INC. 191 SPRING STREET LEXINGTON MA 02421 0 1 0 0 Chief Security & Res. Officer Restricted Share Units 2020-10-01 4 A 0 15899 0.00 A 15899 D Share Option (Right to Buy) 47.17 2020-10-01 4 A 0 36912 0.00 A 2030-10-01 Ordinary Shares 36912 36912 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 1, 2020. Twenty-five percent (25%) of the units vest on October 1, 2021 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. This option was granted on October 1, 2020. Twenty-five percent (25%) of the shares vest on October 1, 2021, 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 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 September 21, 2020). /s/ Robert P. Nault, Attorney-in-Fact 2020-10-05