Del. Code tit. 25, § 109

If a conveyance of lands, tenements or hereditaments is absolute on its face and there is a defeasance, or written contract in the nature of a defeasance, or for a reconveyance of the premises, or any part thereof, the person to whom such conveyance is made shall cause to be indorsed thereon, and recorded therewith, a note stating that there is such defeasance, or contract, and the general purport of it, or the recording of such conveyance shall be of no effect. Such defeasance, or contract, shall be duly acknowledged, or proved, and recorded in the recorder’s office for the county wherein such lands, tenements or hereditaments are situate within 60 days after the day of making the same, or it shall not avail against a fair creditor, mortgagee or purchaser for a valuable consideration of or from the person to whom such conveyance is made, unless it appears that such creditor, when giving the credit, or such mortgagee or purchaser when advancing the consideration, had notice of such defeasance, or contract. Such contract, although not under seal, may be acknowledged or proved in the same manner as a deed.