Statement of Changes in Beneficial Ownership (4)

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

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Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940

1. Name and Address of Reporting Person * Anderson Karen M.	2. Issuer Name and Ticker or Trading Symbol Mimecast Ltd [ MIME ]	5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director                    _____ 10% Owner __X__ Officer (give title below)    _____ Other (specify below) Chief Human Resources Officer
(Last)          (First)          (Middle) C/O MIMECAST NORTH AMERICA, INC., 191 SPRING STREET	3. Date of Earliest Transaction (MM/DD/YYYY) 2/1/2022
(Street) LEXINGTON, MA 02421 (City)        (State)        (Zip)	4. If Amendment, Date Original Filed (MM/DD/YYYY)	6. Individual or Joint/Group Filing (Check Applicable Line) _X _ Form filed by One Reporting Person ___ Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1.Title of Security (Instr. 3)	2. Trans. Date	2A. Deemed Execution Date, if any	3. Trans. 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	2/1/2022		M		4333 (1)	A	(2)	4333	D
Restricted Share Units (2)	2/1/2022		F		1917 (3)	D	$79.74 (4)	10583 (5)	D
Restricted Share Units (2)	2/1/2022		M		4333 (6)	D	(2)	6250 (5)	D
Restricted Share Units (2)								9549 (7)	D
Restricted Share Units (2)								12239 (8)	D
Restricted Share Units (2)								9400 (9)	D

Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivate Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Trans. Date	3A. Deemed Execution Date, if any	4. Trans. 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		7. Title and Amount of Securities Underlying Derivative Security (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

Explanation of Responses:
(1)	The number of Ordinary Shares reflects the settlement of restricted share units upon vesting, net of Ordinary Shares that were retained (but not issued) by the Issuer in satisfaction of tax withholding obligations associated with the vesting of such units.
(2)	Each restricted share unit represents a contingent right to receive one share of the Issuer's Ordinary Shares.
(3)	The restricted share units reported as disposed of herein reflect the number of Ordinary Shares underlying the restricted share units that were retained (but not issued) by the Issuer in satisfaction of tax withholding obligations associated with the vesting of such units.
(4)	Price reflects the closing price of the Issuer's Ordinary Shares on the Nasdaq Global Select Market on February 1, 2022.
(5)	These restricted share units were granted on February 1, 2019. Twenty-five percent (25%) of the units vested on February 1, 2020, twenty-five percent (25%) of the units vested on February 1, 2021, twenty-five percent (25%) of the units vested on February 1, 2022, and the remainder of the units vest on February 1, 2023, provided that the Reporting Person remains an employee of the Issuer on such vesting date.
(6)	The restricted share units reported as disposed of herein were settled for the Issuer's Ordinary Shares upon the vesting of such units (as reported in Row 1 above).
(7)	These restricted share units were granted on April 1, 2020. Twenty-five percent (25%) of the units vested on April 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.
(8)	These restricted share units were granted on April 1, 2021. Twenty-five percent (25%) of the units vest on April 1, 2022 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.
(9)	These restricted share units were granted on July 1, 2021. Twenty-five percent (25%) of the units vest on July 1, 2022 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.

Remarks: 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 January 3, 2019).

Reporting Owners
Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
Anderson Karen M. C/O MIMECAST NORTH AMERICA, INC. 191 SPRING STREET LEXINGTON, MA 02421			Chief Human Resources Officer

Signatures
/s/ Robert P. Nault, Attorney-in-Fact		2/2/2021
**Signature of Reporting Person		Date