Ownership Submission
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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(Print or Type Responses)
1. Name and Address of Reporting Person *
Bauer Peter
  2. Issuer Name and Ticker or Trading Symbol
Mimecast Ltd [MIME]
5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
__X__ Director _____ 10% Owner
__X__ Officer (give title below) _____ Other (specify below)
Chief Executive Officer
(Last)
(First)
(Middle)
C/O MIMECAST NORTH AMERICA, INC., 191 SPRING STREET
3. Date of Earliest Transaction (Month/Day/Year)
04/01/2019
(Street)

LEXINGTON, MA 02421
4. If Amendment, Date Original Filed(Month/Day/Year)
6. Individual or Joint/Group Filing(Check Applicable Line)
_X_ Form filed by One Reporting Person
___ 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 04/02/2019   M   1,596 (1) A (2) 46,596 D  
Restricted Share Units (2) 04/02/2019   F   654 (3) D $ 49.62 (4) 8,346 (5) D  
Restricted Share Units (2) 04/02/2019   M   1,596 (6) D (2) 6,750 (5) D  
Restricted Share Units (2) 04/01/2019   A   18,000 (7) A $ 0 18,000 (7) D  
Ordinary Shares               2,227,500 I By Rock Trustees Limited (8)
Ordinary Shares               1,799,376 I By Declaration of Trust of Peter Bauer (9)

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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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
Share Option (Right to Buy) $ 47.23 04/01/2019   A   36,000     (10) 04/01/2029 Ordinary Shares 36,000 $ 0 36,000 (10) D  

Reporting Owners

Reporting Owner Name / Address Relationships
 Director  10% Owner  Officer  Other
Bauer Peter
C/O MIMECAST NORTH AMERICA, INC.
191 SPRING STREET
LEXINGTON, MA 02421
  X     Chief Executive Officer  

Signatures

 /s/ Robert P. Nault, Attorney-in-Fact   04/03/2019
**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) 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 April 2, 2019.
(5) 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.
(6) The restricted share units reported as disposed of herein were settled for the Issuer's Ordinary Shares upon the vesting of such units.
(7) 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 such vesting date.
(8) 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.
(9) 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.
(10) This option was granted on April 1, 2019. Twenty-five percent (25%) of the shares vest on April 1, 2020, 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 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 April 2, 2018).

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