I rent an apartment. The landlord sold the property, and despite several letters, I have been unable to obtain the new owner’s contact details in order to pay the rent. Is this lawful?

No. The law expressly provides that: “in the event of a transfer of the dwelling, whether for consideration or free of charge, the new landlord must notify the tenant of his or her name or corporate name and address or registered office and, where applicable, those of his or her representative” (Article 3 of Law No. 89-462 of 6 July 1989).