The statute at issue is a mess: "C. Notice of intent to enter shall (i) be sent to the owner by certified mail, (ii) set forth the date of the intended entry, and (iii) be made not less than 15 days prior to the date of mailing of the notice of intent to enter."
Presumably, what was intended was a parallel to this: "B. A request for permission to inspect shall (i) be sent to the owner by certified mail, (ii) set forth the date such inspection is proposed to be made, and (iii) be made not less than 15 days prior to the date of the proposed inspection."
So, in C., the legislature wrote "mailing of the notice of intent to enter" when they almost certainly intended "date of the intended entry," just as they intended "date of the proposed inspection" in the preceding paragraph.
But, why would "made" mean the same thing as "sent" in a sentence where both are used?
Randomly, the Supreme Court of the United States has taken up the meaning of "shall be made," in a recent decision:
What remains is the phrase “shall be made.” “[S]hall be made” is a form of the verb “to make,” which means “to bring into existence,” “to produce,” “to render,” and “to cause to be or become.” Random House Dictionary of the English Language, at 866. Thus, “shall be made ” means “shall be produced,” etc.
Babb v. Wilkie, No. 18-882, 2020 WL 1668281, at *5 (U.S. Apr. 6, 2020).
Perhaps in this sense a written notice could be "made" by having been "brought into existence" or "produced" not less than 15 days before mailing, but that would be silly. In my experience that only happens when I put the mail in my car and forget that it is there and drive around with it for a while.