Mass. Gen. Laws ch. 244, § 10: Foreclosure and redemption where entry made before breach

Section 10. A mortgagee, or a person claiming under him in possession under the preceding section, may, after breach of condition, make a new formal entry for breach of condition, or bring an action, under section one, with the same effect as if he were not in possession; or he may foreclose the right of redemption by giving, after breach of condition, to the mortgagor, or person claiming under him, a written notice that he will thenceforward hold the land for the purpose of foreclosure and causing a certificate in proof thereof to be recorded within thirty days after such notice as in case of an original entry. If such notice is given and recorded, the three years limited for redemption shall run from the date of giving the notice.