UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 6-K

Report of Foreign Private Issuer

Pursuant to Rule 13a-16 or 15d-16

of the Securities Exchange Act of 1934

July 7, 2017

Commission File No. 001-37637

MIMECAST LIMITED

CityPoint, One Ropemaker Street, Moorgate

London EC2Y 9AW

United Kingdom

Tel: +44 0207 847 8700

(Address, Including ZIP Code, and Telephone Number, Including Area Code, of Registrant’s Principal Executive Offices)

Indicate by check mark whether the registrant files or will file annual reports under cover of Form 20-F or Form 40-F.

Form 20-F ☒             Form 40-F ☐

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(1):   ☐

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(7):   ☐

On July 7, 2017, Mimecast Limited (the “Company”) announced its 2017 annual general meeting of shareholders and made available to its shareholders certain other materials in connection with such meeting.

Such materials are attached as exhibits to this Form 6-K and are incorporated by reference herein.

Shareholders who acquire beneficial interests in the Company’s shares, after the date hereof and before the date of the 2017 annual general meeting may request copies of these materials from the Company’s transfer agent and registrar, at Computershare, P.O. Box 505000, Louisville, KY 40233-5000, USA (781-575-3100) or from the Company at 480 Pleasant Street, Watertown, MA 02472. Such shareholders must return the form of proxy (duly signed and together with any power of attorney or other authority under which it is signed) by post or (during normal business hours only) by hand at the offices of the Company’s registrars, Computershare, P.O. Box 505008, Louisville, KY 40233-9814, USA no later than 11:59 pm (London time) on August 2, 2017 (or, if the meeting is adjourned, no later than 48 hours (excluding nonworking days) before the time of any adjourned meeting).

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

	MIMECAST LIMITED
Date: July 7, 2017	By:	/s/ Peter Campbell
		Peter Campbell
		Chief Financial Officer

EXHIBIT INDEX

Exhibit	Description of Exhibit
99.1	Notice of the 2017 Annual General Meeting of Shareholders
99.2	Explanatory Notes on the Business of the Annual General Meeting
99.3	2017 Annual General Meeting Proxy Card