X0306 4 2020-04-01 0 0001644675 Mimecast Ltd MIME 0001676397 Bauer Peter C/O MIMECAST NORTH AMERICA, INC. 191 SPRING STREET LEXINGTON MA 02421 1 1 0 0 Chief Executive Officer Ordinary Shares 125000 D Ordinary Shares 2142500 I By Rock Trustees Limited Ordinary Shares 1524376 I By Declaration of Trust of Peter Bauer Restricted Share Units 6750 D Restricted Share Units 18000 D Share Option (Right to Buy) 33.38 2020-04-01 4 A 0 244997 0.00 A 2030-04-01 Ordinary Shares 244997 244997 D These shares are held by Rock Trustees Limited as trustee of the Butterworth Trust (the "Butterworth Trust"), of which the Reporting Person is a beneficiary. As trustee of the Butterworth Trust, Rock Trustees Limited exercises dispositive power over the shares held therein. The Reporting Person disclaims Section 16 beneficial ownership of the shares held by the Butterworth Trust, except to the extent, if any, of his pecuniary interest therein. These shares are held by the Declaration of Trust of Peter Bauer. The Reporting Person is a beneficiary, and the sole trustee of, the Declaration of Trust of Peter Bauer. 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 2, 2018. Twenty-five percent (25%) of the units vested on April 2, 2019, 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. 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 each such vesting date. This option was granted on April 1, 2020. Twenty-five percent (25%) of the shares vest on April 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 April 2, 2018). /s/ Robert P. Nault, Attorney-in-Fact 2020-04-01