Sec Form 3 Filing - SUMMIT PARTNERS L P @ EngageSmart, Inc. - 2021-09-23

FORM 3 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 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 SUMMIT PARTNERS L P 2. Issuer Name and Ticker or Trading Symbol EngageSmart, Inc. [ ESMT] 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) 222 BERKELEY STREET, 18TH FLOOR 3. Date of Earliest Transaction (MM/DD/YY) 09/23/2021 (Street) BOSTON, MA02116 4. If Amendment, Date Original Filed (MM/DD/YY) 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 (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 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 Common Stock, par value $0.001 per share 26,926,752 ( 1 ) I See Footnotes ( 2 ) ( 3 ) ( 4 )

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 (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 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 (MM/DD/YY) 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 SUMMIT PARTNERS L P 222 BERKELEY STREET, 18TH FLOOR BOSTON, MA02116 X Summit Partners Growth Equity Fund VIII-A, L.P. 222 BERKELEY STREET, 18TH FLOOR BOSTON, MA02116 X Summit Partners Growth Equity Fund VIII-B, L.P. 222 BERKELEY STREET, 18TH FLOOR BOSTON, MA02116 X Summit Partners Entrepreneur Advisors Fund I, L.P. 222 BERKELEY STREET, 18TH FLOOR BOSTON, MA02116 X Summit Investors I, LLC 222 BERKELEY STREET, 18TH FLOOR BOSTON, MA02116 X Summit Investors I (UK), L.P. 222 BERKELEY STREET, 18TH FLOOR BOSTON, MA02116 X SUMMIT MASTER COMPANY, LLC 222 BERKELEY STREET, 18TH FLOOR BOSTON, MA02116 X CHUNG PETER Y 222 BERKELEY STREET, 18TH FLOOR BOSTON, MA02116 X MANNION MARTIN J 222 BERKELEY STREET, 18TH FLOOR BOSTON, MA02116 X Signatures /s/ Robin W. Devereux's, as attorney-in-fact for Summit Partners Growth Equity Fund VIII-A, L.P. 09/23/2021 Signature of Reporting Person Date /s/ Robin W. Devereux's, as attorney-in-fact for Summit Partners Growth Equity Fund VIII-B, L.P. 09/23/2021 Signature of Reporting Person Date /s/ Robin W. Devereux's, as attorney-in-fact for Summit Partners Entrepreneur Advisors Fund I, L.P. 09/23/2021 Signature of Reporting Person Date /s/ Robin W. Devereux's, as attorney-in-fact for Summit Investors I, LLC 09/23/2021 Signature of Reporting Person Date /s/ Robin W. Devereux's, as attorney-in-fact for Summit Investors I (UK), L.P. 09/23/2021 Signature of Reporting Person Date /s/ Robin W. Devereux's, as attorney-in-fact for Summit Partners, L.P. 09/23/2021 Signature of Reporting Person Date /s/ Robin W. Devereux's, as attorney-in-fact for Summit Master Company, LLC 09/23/2021 Signature of Reporting Person Date /s/ Robin W. Devereux's, as attorney-in-fact for Peter Y. Chung 09/23/2021 Signature of Reporting Person Date /s/ Robin W. Devereux's, as attorney-in-fact for Martin J. Mannion 09/23/2021 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Consists of (i) 19,327,768 shares of common stock held by Summit Partners Growth Equity Fund VIII-A, L.P., (ii) 7,060,848 shares of common stock held by Summit Partners Growth Equity Fund VIII-B, L.P., (iii) 128,222 shares of common stock held by Summit Partners Entrepreneur Advisors Fund I, L.P., (iv) 370,024 shares of common stock held by Summit Investors I, LLC and (v) 39,890 shares of common stock held by Summit Investors I (UK), L.P. ( 2 )Summit Partners, L.P. is the managing member of Summit Partners GE VIII, LLC, which is the general partner of Summit Partners GE VIII, L.P., which is the general partner of each of Summit Partners Growth Equity Fund VIII-A, L.P. and Summit Partners Growth Equity Fund VIII-B, L.P. ( 3 )Summit Master Company, LLC is the (A) sole managing member of Summit Partners Entrepreneur Advisors GP, LLC, which is the general partner of Summit Partners Entrepreneur Advisors Fund I, L.P., and (B) the managing member of Summit Investors Management, LLC, which is the manager of Summit Investors I, LLC and the general partner of Summit Investors I (UK), L.P. Summit Master Company, LLC, as the sole managing member of Summit Partners Entrepreneur Advisors GP, LLC and the managing member of Summit Investors Management, LLC, has delegated investment decisions, including voting and dispositive power, to Summit Partners, L.P. and its Investment Committee. Summit Partners, L.P., through a two-person Investment Committee currently composed of Martin J. Mannion and Peter Y. Chung, has voting and dispositive authority over the shares held by each of these entities and therefore beneficially owns such shares. ( 4 )(Continued from footnote 3) Each of the entities affiliated with Summit Partners, L.P. that are mentioned herein and each of Mr. Mannion and Mr. Chung disclaims beneficial ownership of the shares of common stock, in each case, except to the extent of it or his pecuniary interest therein.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* 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).

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