Exhibit (b)

SECTION 906 CERTIFICATIONS

In connection with this report on Form N-CSR for the Registrant as furnished to the Securities and Exchange Commission on the date hereof (the “Report”), the undersigned hereby certifies, pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that:

(1) the Report fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934, as applicable; and

(2) the information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Registrant.

By:	/s/ Kirk C. Lehneis
	Kirk C. Lehneis President and Principal Executive Officer, MainStay MacKay DefinedTerm Municipal Opportunities Fund
Date: August 5, 2024

SECTION 906 CERTIFICATIONS

In connection with this report on Form N-CSR for the Registrant as furnished to the Securities and Exchange Commission on the date hereof (the “Report”), the undersigned hereby certifies, pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that:

(1) the Report fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934, as applicable; and

(2) the information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Registrant.

By:	/s/ Jack R. Benintende
	Jack R. Benintende Treasurer and Principal Financial and Accounting Officer, MainStay MacKay DefinedTerm Municipal Opportunities Fund
Date: August 5, 2024