Press Release (1/3/22): Monthly Dividend Distributions for the Months of January, February, March

MAINSTAY MACKAY DEFINEDTERM MUNICIPAL OPPORTUNITIES FUND DECLARES MONTHLY DIVIDEND DISTRIBUTIONS FOR THE MONTHS OF

JANUARY, FEBRUARY AND MARCH 2022

NEW YORK, January 3, 2022 - MainStay MacKay DefinedTerm Municipal Opportunities Fund (the "Fund") (NYSE:MMD) today announced monthly dividend distributions of $0.085 per common share for the months of January, February and March 2022. This amount is consistent with the Fund's October, November and December 2021 dividend distribution, which was also $0.085 per common share.

Portfolio and municipal market commentary will be published on or around January 3, 2022 and can be retrieved here.

Dividend Distribution Schedule:

Month	Declaration Date	Ex-Date	Record Date	Payable Date
October	1/3/2022	1/13/2022	1/14/2022	1/31/2022
November	1/3/2022	2/14/2022	2/15/2022	2/28/2022
December	1/3/2022	3/14/2022	3/15/2022	3/31/2022

The Fund's dividend will be derived from its monthly undistributed net investment income and is not expected to contain any retuof principal.

The Fund's daily New York Stock Exchange closing prices, net asset values per share, as well as other information are available by clicking hereor by calling the Fund's shareholder servicing agent at (855) 456-9683.

For more insights from MacKay Municipal Managers™ and our New York Life Investments affiliates click here.

There are risks inherent in any investment, including market risk, interest rate risk, credit risk and the possible loss of principal. There can be no assurance that the Fund's investment objectives will be achieved. Shares of closed-end funds frequently trade at a discount from their net asset value, which may increase investor risk.

About New York Life Investments

With over $650 billion in Assets Under Management* as of September 30, 2021, New York Life Investmentsis comprised of the affiliated global asset management businesses of its parent company, New York Life Insurance Company (New York Life), and offers clients access to specialized, independent investment teams through its family of affiliated boutiques. New York Life Investments remains committed to clients through a combination of the diverse perspectives of its boutiques and a long-lasting focus on sustainable relationships.

New York Life Insurance Company (www.newyorklife.com), a Fortune 100 company founded in 1845, is the largest mutual life insurance company in the United States** and one of the largest life insurers in the world. Headquartered in New York City, New York Life's family of companies offers life insurance, retirement income, investments and long-term care insurance. New York Life has the highest financial strength ratings currently awarded to any U.S. life insurer from all four of the major credit rating agencies***.

*AUM includes assets of Investment Advisors affiliated with New York Life Insurance Company as of September 30, 2021. AUM for Candriam and Ausbil is reported at the spot rate.

• Based on revenue as reported by "Fortune 500 ranked within Industries, Insurance: Life, Health (Mutual)," Fortune magazine, 6/2/2021. For methodology, please seehttp://fortune.com/fortune500/.

***Individual independent rating agency commentary as of 10/15/2020: A.M. Best (A++), Fitch (AAA), Moody's Investors Service (Aaa), Standard & Poor's (AA+) The financial strength of New York Life Insurance Company applies only to its insurance products and not to investment products which are subject to market risk and fluctuation in value.

"New York Life Investments" is both a service mark, and the common trade name, of certain investment advisors affiliated with New York Life Insurance Company.

About MacKay Shields LLC

MacKay Shields LLC (together with its subsidiaries, "MacKay")*, a New York Life Investments Company, is a global asset management firm with $164 billion in assets under management as of September 30, 2021. MacKay manages fixed income and equity strategies for high-net worth individuals and institutional clients, through separately managed accounts and collective investment vehicles including private funds, UCITS, ETFs, closed end funds and mutual funds. MacKay maintains offices in New York City, Princeton, Los Angeles, London and Dublin. For more information, please visit www.mackayshields.comor follow us on Twitteror LinkedIn.

*MacKay Shields is a wholly owned subsidiary of New York Life Investment Management Holdings LLC, which is wholly owned by New York Life Insurance Company.

Media Contact:

Allison Scott | New York Life | (212) 576-4517 | [email protected]

Investors Contact:

855-456-9683

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