MIME 2018 Proxy Statement

SECURITY OWNERSHIP OF CERTAIN BENEFICIAL OWNERS AND MANAGEMENT The following table sets forth certain information known to us regarding the beneficial ownership of our ordinary shares as of June 30, 2018, for: • each person, or group of affiliated persons, who is known by us to beneficially own more than 5% of our ordinary shares; • our named executive officers; • each of our directors and director nominees; and • all executive officers and directors as a group. Beneficial ownership is determined in accordance with the rules of the SEC and generally includes voting or investment power with respect to securities. Except as noted by footnote, and subject to community property laws where applicable, we believe, based on the information provided to us, that the persons and entities named in the table below have sole voting and investment power with respect to all ordinary shares shown as beneficially owned by them. The table lists applicable percentage ownership based on 59,599,656 ordinary shares outstanding as of June 30, 2018, unless indicated otherwise. Options to purchase ordinary shares that are exercisable, and ordinary shares that may be acquired upon the vesting of restricted share units, in each case, within 60 days of June 30, 2018, are deemed to be beneficially owned by the persons holding these options or restricted share units, as applicable, for the purpose of computing percentage ownership of that person, but are not treated as outstanding for the purpose of computing any other person’s ownership percentage. Unless otherwise indicated, the address for each beneficial owner is c/o Mimecast Limited, CityPoint, One Ropemaker Street, Moorgate, London EC2Y 9AW, United Kingdom. Ordinary Shares beneficially owned Name of beneficial owner Number Percentage 5% shareholders: Abdiel Capital Management, LLC (1) . . . . . . . . . . . . . . . . . . . . . . . . 4,924,658 8.3% Entities affiliated with Insight Venture Partners (2) . . . . . . . . . . . . . 9,507,752 16.0% Named executive officers and directors: Peter Bauer (3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4,444,250 7.4% Peter Campbell (4) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 363,587 * Neil Murray (5) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2,633,822 4.4% Edward Jennings (6) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267,318 * Janet Bishop-Levesque . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . — — Robert P. Nault (7) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67,374 * Aron Ain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3,086 * Christopher FitzGerald (8) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121,821 * Jeffrey Lieberman (2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9,507,752 16.0% Hagi Schwartz (9) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29,617 * Stephen Ward . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . — — All executive officers and directors as a group (13 persons) (10) . . . . 17,501,330 29.0% (*) Represents beneficial ownership of less than 1%. (1) This ownership information is as of December 31, 2017 and is based solely on a Schedule 13G/A filed by Abdiel Capital Management, LLC (“Abdiel Capital”) with the SEC on January 31, 2018. The ownership 20