FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person * Insight Holdings Group, LLC   2. Issuer Name and Ticker or Trading Symbol Mimecast Ltd [MIME] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director __X__ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) C/O INSIGHT VENTURE PARTNERS, 1114 AVENUE OF THE AMERICAS, 36TH FLOOR 3. Date of Earliest Transaction (Month/Day/Year) 02/20/2019 (Street) NEW YORK, NY 10036 4. If Amendment, Date Original Filed(Month/Day/Year) 6. Individual or Joint/Group Filing(Check Applicable Line) ___ Form filed by One Reporting Person _X_ Form filed by More than One Reporting Person (City) (State) (Zip) Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned

1.Title of Security (Instr. 3) 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Ordinary Shares 02/20/2019   J(1)   475,528 D (1) 1,809,948 I See footnote (2) Ordinary Shares 02/20/2019   J(1)   209,337 D (1) 796,779 I See footnote (3) Ordinary Shares 02/20/2019   J(1)   30,078 D (1) 114,486 I See footnote (4) Ordinary Shares 02/20/2019   J(1)   11,006 D (1) 41,894 I See footnote (5) Ordinary Shares 02/20/2019   J(1)   524,051 D (1) 1,994,645 I See footnote (6) Ordinary Shares 02/20/2019   J(1)   20,356 D (1) 20,356 I See footnote (7) Ordinary Shares 02/20/2019   J(1)   5,233 D (1) 19,885 I See footnote (8)

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Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)

1. Title of Derivative Security (Instr. 3)

2. Conversion or Exercise Price of Derivative Security

3. Transaction Date (Month/Day/Year)

3A. Deemed Execution Date, if any (Month/Day/Year)

4. Transaction Code (Instr. 8)

5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5)

6. Date Exercisable and Expiration Date (Month/Day/Year)

7. Title and Amount of Underlying Securities (Instr. 3 and 4)

8. Price of Derivative Security (Instr. 5)

9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)

10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4)

11. Nature of Indirect Beneficial Ownership (Instr. 4)

Code

V

(A)

(D)

Date Exercisable

Expiration Date

Title

Amount or Number of Shares

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
Insight Holdings Group, LLC C/O INSIGHT VENTURE PARTNERS 1114 AVENUE OF THE AMERICAS, 36TH FLOOR NEW YORK, NY 10036		X
Insight Venture Partners VII, L.P. INSIGHT VENTURE ASSOCIATES VII, L.P. 1114 AVENUE OF THE AMERICAS, 36TH FLOOR NEW YORK, NY 10036		X
Insight Venture Partners (Cayman) VII, L.P. C/O INSIGHT VENTURE PARTNERS 1114 AVENUE OF THE AMERICAS, 36TH FLOOR NEW YORK, NY 10036		X
Insight Venture Partners (Delaware) VII, L.P. C/O INSIGHT VENTURE PARTNERS 1114 AVENUE OF THE AMERICAS, 36TH FLOOR NEW YORK, NY 10036		X
Insight Venture Partners VII (Co-Investors), L.P. C/O INSIGHT VENTURE PARTNERS 1114 AVENUE OF THE AMERICAS, 36TH FLOOR NEW YORK, NY 10036		X
Insight Venture Associates VII, L.P. C/O INSIGHT VENTURE PARTNERS 1114 AVENUE OF THE AMERICAS, 36TH FLOOR NEW YORK, NY 10036		X
Insight Venture Associates VII, Ltd. C/O INSIGHT VENTURE PARTNERS 1114 AVENUE OF THE AMERICAS, 36TH FLOOR NEW YORK, NY 10036		X
Insight Venture Partners Coinvestment Fund II, L.P. C/O INSIGHT VENTURE PARTNERS 1114 AVENUE OF THE AMERICAS, 36TH FLOOR NEW YORK, NY 10036		X
Insight Venture Associates Coinvestment II, L.P. C/O INSIGHT VENTURE PARTNERS 1114 AVENUE OF THE AMERICAS, 36TH FLOOR NEW YORK, NY 10036		X
IVP (Venice), L.P. C/O INSIGHT VENTURE PARTNERS 1114 AVENUE OF THE AMERICAS, 36TH FLOOR NEW YORK, NY 10036		X

Signatures

Insight Holdings Group, LLC, By: Blair Flicker, Attorney-in-Fact, /s/ Blair Flicker		02/22/2019
**Signature of Reporting Person		Date

Explanation of Responses:

*	If the form is filed by more than one reporting person, see Instruction 4(b)(v).
**	Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1)	See Exhibit 99.1
(2)	See Exhibit 99.1
(3)	See Exhibit 99.1
(4)	See Exhibit 99.1
(5)	See Exhibit 99.1
(6)	See Exhibit 99.1
(7)	See Exhibit 99.1
(8)	See Exhibit 99.1
Remarks: Exhibit List ------------ Exhibit 99.1 - Explanation of Responses Exhibit 99.2 - Joint Filers' Signatures Exhibit 99.3 - Joint Filer Information

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