X0306 4 2019-04-04 0 0001644675 Mimecast Ltd MIME 0001328837 Lieberman Jeffrey C/O INSIGHT VENTURE PARTNERS 1114 AVENUE OF THE AMERICAS, 36TH FLOOR NEW YORK NY 10036 1 0 0 0 Ordinary Shares 2019-04-04 4 J 0 27980 A 184039 D Ordinary Shares 2019-04-04 4 J 0 1473056 D 108720 I See Footnotes The distributions reported on this Form 4 were automatically effected pursuant to a Rule 10b5-1 distribution plan entered into by the Insight Funds (as defined in Exhibit 99.1) on September 14, 2018. See Exhibit 99.1 See Exhibit 99.1 See Exhibit 99.1 See Exhibit 99.1 See Exhibit 99.1 Exhibit List Exhibit 99.1 - Explanation of Responses /s/ Jeffrey Lieberman 2019-04-08