SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13G

(Rule 13d-102)

INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT TO

RULES 13d-1(b),

(c), AND (d) AND AMENDMENTS THERETO FILED PURSUANT TO RULE 13d-2

(Amendment No. 3)*

MIMECAST LIMITED

(Name of Issuer)

ORDINARY SHARES, $0.012 NOMINAL VALUE

(Title of Class of Securities)

G14838109

(CUSIP Number)

December 31, 2019

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

☐ Rule 13d-1(b)

☐ Rule 13d-1(c)

☒ Rule 13d-1(d)

*	The remainder of this cover page shall be filled out for a reporting person’s initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter the disclosures provided in a prior cover page.

The information required in the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

CUSIP No. G14838109

13G

Page 2 of 15 Pages


1.	NAMES OF REPORTING PERSONS Insight Venture Partners VII, L.P.
2.	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS) (a) ☐ (b) ☒
3.	SEC USE ONLY
4.	CITIZENSHIP OR PLACE OF ORGANIZATION Cayman Islands
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH		5.	SOLE VOTING POWER 0
		6.	SHARED VOTING POWER 0
		7.	SOLE DISPOSITIVE POWER 0
		8.	SHARED DISPOSITIVE POWER 0
9.	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 0
10.	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS) ☐
11.	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9 0.0%
12.	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS) PN

CUSIP No. G14838109

13G

Page 3 of 15 Pages


1.	NAMES OF REPORTING PERSONS Insight Venture Partners (Cayman) VII, L.P.
2.	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS) (a) ☐ (b) ☒
3.	SEC USE ONLY
4.	CITIZENSHIP OR PLACE OF ORGANIZATION Cayman Islands
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH		5.	SOLE VOTING POWER 0
		6.	SHARED VOTING POWER 0
		7.	SOLE DISPOSITIVE POWER
		8.	SHARED DISPOSITIVE POWER 0
9.	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 0
10.	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS) ☐
11.	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9 0.0%
12.	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS) PN

CUSIP No. G14838109				13G	Page 4 of 15 Pages

1.	NAMES OF REPORTING PERSONS Insight Venture Partners (Delaware) VII, L.P.
2.	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS) (a) ☐ (b) ☒
3.	SEC USE ONLY
4.	CITIZENSHIP OR PLACE OF ORGANIZATION Delaware
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH		5.	SOLE VOTING POWER 0
		6.	SHARED VOTING POWER 0
		7.	SOLE DISPOSITIVE POWER 0
		8.	SHARED DISPOSITIVE POWER 0
9.	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 0
10.	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS) ☐
11.	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9 0.0%
12.	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS) PN

CUSIP No. G14838109				13G	Page 5 of 15 Pages

1.	NAMES OF REPORTING PERSONS Insight Venture Partners VII (Co-Investors), L.P.
2.	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS) (a) ☐ (b) ☒
3.	SEC USE ONLY
4.	CITIZENSHIP OR PLACE OF ORGANIZATION Cayman Islands
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH		5.	SOLE VOTING POWER 0
		6.	SHARED VOTING POWER 0
		7.	SOLE DISPOSITIVE POWER 0
		8.	SHARED DISPOSITIVE POWER 0
9.	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 0
10.	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS) ☐
11.	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9 0.0%
12.	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS) PN


CUSIP No. G14838109				13G	Page 6 of 15 Pages

1.	NAMES OF REPORTING PERSONS Insight Venture Partners Coinvestment Fund II, L.P.
2.	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS) (a) ☐ (b) ☒
3.	SEC USE ONLY
4.	CITIZENSHIP OR PLACE OF ORGANIZATION Delaware
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH		5.	SOLE VOTING POWER 0
		6.	SHARED VOTING POWER 0
		7.	SOLE DISPOSITIVE POWER 0
		8.	SHARED DISPOSITIVE POWER 0
9.	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 0
10.	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS) ☐
11.	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9 0.0%
12.	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS) PN

CUSIP No. G14838109				13G	Page 7 of 15 Pages

1.	NAMES OF REPORTING PERSONS Insight Venture Associates Coinvestment II, L.P.
2.	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS) (a) ☐ (b) ☒
3.	SEC USE ONLY
4.	CITIZENSHIP OR PLACE OF ORGANIZATION Delaware
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH		5.	SOLE VOTING POWER 0
		6.	SHARED VOTING POWER 0
		7.	SOLE DISPOSITIVE POWER 0
		8.	SHARED DISPOSITIVE POWER 0
9.	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 0
10.	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS) ☐
11.	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9 0.0%
12.	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS) PN

CUSIP No. G14838109				13G	Page 8 of 15 Pages

1.	NAMES OF REPORTING PERSONS Insight Venture Associates VII, L.P.
2.	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS) (a) ☐ (b) ☒
3.	SEC USE ONLY
4.	CITIZENSHIP OR PLACE OF ORGANIZATION Cayman Islands
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH		5.	SOLE VOTING POWER 0
		6.	SHARED VOTING POWER 0
		7.	SOLE DISPOSITIVE POWER 0
		8.	SHARED DISPOSITIVE POWER 0
9.	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 0
10.	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS) ☐
11.	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9 0.0%
12.	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS) PN

CUSIP No. G14838109				13G	Page 9 of 15 Pages

1.	NAMES OF REPORTING PERSONS Insight Venture Associates VII, Ltd.
2.	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS) (a) ☐ (b) ☒
3.	SEC USE ONLY
4.	CITIZENSHIP OR PLACE OF ORGANIZATION Cayman Islands
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH		5.	SOLE VOTING POWER 0
		6.	SHARED VOTING POWER 0
		7.	SOLE DISPOSITIVE POWER 0
		8.	SHARED DISPOSITIVE POWER 0
9.	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 0
10.	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS) ☐
11.	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9 0.0%
12.	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS) CO

CUSIP No. G14838109				13G	Page 10 of 15 Pages

1.	NAMES OF REPORTING PERSONS Insight Holdings Group, LLC
2.	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS) (a) ☐ (b) ☒
3.	SEC USE ONLY
4.	CITIZENSHIP OR PLACE OF ORGANIZATION Delaware
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH		5.	SOLE VOTING POWER 0
		6.	SHARED VOTING POWER 0
		7.	SOLE DISPOSITIVE POWER 0
		8.	SHARED DISPOSITIVE POWER 0
9.	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 0
10.	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS) ☐
11.	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9 0.0%
12.	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS) OO

Item 1(a).

Name of Issuer:

Mimecast Limited (the “Issuer”)

Item 1(b).

Address of Issuer’s Principal Executive Offices:

CityPoint, One Ropemaker Street, Moorgate

London EC2Y 9AW

United Kingdom

Item 2(a).

Name of Person Filing:

This Statement is being filed by the following persons (each a “Reporting Person” and, collectively, the “Reporting Persons”): (i) Insight Venture Partners VII, L.P., a Cayman Islands exempted limited partnership (“IVP”); (ii) Insight Venture Partners (Cayman) VII, L.P., a Cayman Islands exempted limited partnership (“IVP Cayman”); (iii) Insight Venture Partners (Delaware) VII, L.P., a Delaware limited partnership (“IVP Delaware”); (iv) Insight Venture Partners VII (Co-Investors), L.P., a Cayman Islands exempted limited partnership (“IVP Co-Investors” and together with IVP, IVP Cayman, and IVP Delaware, the “Insight VII Funds”); (v) Insight Venture Partners Coinvestment Fund II, L.P., a Delaware limited partnership (“IVP Co-Investment Fund II”); (vi) Insight Venture Associates Coinvestment II, L.P., a Delaware limited partnership (“IVP Associates Co-Investment”); (vii) Insight Venture Associates VII, L.P., a Cayman Islands exempted limited partnership (“IVA”); (viii) Insight Venture Associates VII, Ltd., a Cayman Islands exempted company (“IVA Ltd”); and (ix) Insight Holdings Group, LLC, a Delaware limited liability company (“Insight Holdings”). The general partner of each of the Insight VII Funds is IVA, whose general partner is IVA Ltd. The general partner of IVP Co-Investment Fund II is IVP Associates Co-Investment. The sole shareholder of IVA Ltd and general partner of IVP Associates Co-Investment is Insight Holdings.

Item 2(b).

Address of Principal Business Office or, if None, Residence:

The address of the principal business and principal office of each of the Reporting Persons is c/o Insight Venture Partners, 1114 Avenue of the Americas, 36th Floor, New York, New York 10036.

Item 2(c).

Citizenship:

See Item 2(a).

Item 2(d).

Title of Class of Securities:

Ordinary Shares, nominal value $0.012 per share (“Ordinary Shares”).

Item 2(e).

CUSIP Number:

G14838109

Item 3.

If this statement is filed pursuant to Rule 13d-1(b) or Rule 13d-2(b) or (c), check whether the person filing is a:


(a)	☐	Broker or dealer registered under Section 15 of the Exchange Act.

(b)	☐	Bank as defined in Section 3(a)(6) of the Exchange Act.

(c)	☐	Insurance company as defined in Section 3(a)(19) of the Exchange Act.

(d)	☐	Investment company registered under Section 8 of the Investment Company Act.

(e)	☐	An investment adviser in accordance with Rule 13d-1(b)(1)(ii)(E);

(f)	☐	An employee benefit plan or endowment fund in accordance with Rule 13d-1(b)(1)(ii)(F);

(g)	☐	A parent holding company or control person in accordance with Rule 13d-1(b)(1)(ii)(G);

(h)	☐	A savings association as defined in Section 3(b) of the Federal Deposit Insurance Act;

(i)	☐	A church plan that is excluded from the definition of an investment company under Section 3(c)(14) of the Investment Company Act;

(j)	☐	Group, in accordance with Rule 13d-1(b)(1)(ii)(J).

Not applicable.

Item 4.

Ownership.

The information required by Items 4(a)-(c) is set forth in Rows 5-11 of the cover pages hereto for each Reporting Person and is incorporated herein by reference for each such Reporting Person.

Item 5.

Ownership of Five Percent or Less of a Class.

Yes. As of the date hereof, the Reporting Persons have ceased to be the beneficial owners of more than five percent of the Ordinary Shares.

Item 6.

Ownership of More than Five Percent on Behalf of Another Person.

Not applicable.

Item 7.

Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company.

Not applicable.

Item 8.

Identification and Classification of Members of the Group.

The Reporting Persons are making this single, joint filing because they may be deemed to constitute a “group” within the meaning of Section 13(d)(3) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”). The Reporting Persons disclaim membership in a group and this report shall not be deemed an admission by any of the Reporting Persons that they are or may be members of a “group” for purposes of Rule 13d-5 or for any other purpose.

Item 9.

Notice of Dissolution of Group.

Not applicable.

Item 10.

Certification.

Not applicable.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Date: February 11, 2020

	INSIGHT HOLDINGS GROUP, LLC


	By:	/s/ Blair Flicker
	Name:	Blair Flicker
	Title:	Attorney-in-Fact

	INSIGHT VENTURE PARTNERS VII, L.P.
	By:	Insight Venture Associates VII, L.P., its general partner
	By:	Insight Venture Associates VII, Ltd., its general partner


	By:	/s/ Blair Flicker
	Name:	Blair Flicker
	Title:	Vice President

	INSIGHT VENTURE PARTNERS (CAYMAN) VII, L.P.
	By:	Insight Venture Associates VII, L.P., its general partner
	By:	Insight Venture Associates VII, Ltd., its general partner


	By:	/s/ Blair Flicker
	Name:	Blair Flicker
	Title:	Vice President

	INSIGHT VENTURE PARTNERS (DELAWARE) VII, L.P.
	By:	Insight Venture Associates VII, L.P., its general partner
	By:	Insight Venture Associates VII, Ltd., its general partner


	By:	/s/ Blair Flicker
	Name:	Blair Flicker
	Title:	Vice President

	INSIGHT VENTURE PARTNERS VII (CO-INVESTORS), L.P.
	By:	Insight Venture Associates VII, L.P., its general partner
	By:	Insight Venture Associates VII, Ltd., its general partner


	By:	/s/ Blair Flicker
	Name:	Blair Flicker
	Title:	Vice President

[Signature Page to Schedule 13G]

	INSIGHT VENTURE ASSOCIATES VII, L.P.
	By:	Insight Venture Associates VII, Ltd., its general partner


	By:	/s/ Blair Flicker
	Name:	Blair Flicker
	Title:	Vice President

	INSIGHT VENTURE ASSOCIATES VII, LTD.


	By:	/s/ Blair Flicker
	Name:	Blair Flicker
	Title:	Vice President

	INSIGHT VENTURE PARTNERS COINVESTMENT FUND II, L.P.
	By:	Insight Venture Associates Coinvestment II, L.P., its general partner


	By:	/s/ Blair Flicker
	Name:	Blair Flicker
	Title:	Vice President

	INSIGHT VENTURE ASSOCIATES COINVESTMENT II, L.P.


	By:	/s/ Blair Flicker
	Name:	Blair Flicker
	Title:	Authorized Officer

[Signature Page to Schedule 13G]