EXHIBIT 4.1

Morgan Stanley Smith Barney LLC
2000 Westchester Avenue
Purchase, New York 10577

April 30, 2025

Morgan Stanley Portfolios, Series 81
c/o The Bank of New York Mellon, as Trustee
240 Greenwich Street, 22W Fl
New York, New York 10286

Re: Morgan Stanley Portfolios, Series 81

Ladies and Gentlemen:

We have examined the Registration Statement File No. 333-285632 for the above captioned trust. We hereby consent to the use in the Registration Statement of the references to Morgan Stanley Smith Barney LLC as evaluator.

You are hereby authorized to file a copy of this letter with the Securities and Exchange Commission.

Sincerely,

MORGAN STANLEY SMITH BARNEY LLC

By: /s/ MICHAEL B. WEINER                                          
Executive Director