(a) Except as provided in subdivisions (b) and (c), a person who has undertaken as an agent of a mortgagee, beneficiary, or owner of a promissory note secured directly or collaterally by a mortgage or deed of trust on real property or an estate for years therein, to make collections of payments from an obligor under the note, shall mail the following notices, postage prepaid, to each mortgagee, beneficiary or owner for whom the agent has agreed to make collections from the obligor under the note: