This Halacha is an excerpt from our Sefer
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What should one do if he received a Chametz food in the mail?
One purchased/acquired the Chametz before Pesach: If one purchased and acquired this Chametz before Pesach, then if he performed Mechiras Chametz, it is considered sold to the gentile, and he is to refuse its acceptance, and if it was already received, he is to move it with a broom to the area designated as sold to the gentile. If he did not perform Mechiras Chametz, then the Chametz must be destroyed, as explained in Halacha 6B.
One did not purchase/acquire the Chametz: If during Pesach one was sent Chametz that he did not purchase and never acquired, such as he was sent Chametz from a company for promotion purposes, then it follows the same law as Chametz of a gentile which arrives on Pesach. Thus, he is to refuse to accept it, and if it was already placed on one’s property, then it is to be swept to the public area using a broom. If, however, the company is owned by a Jew, or the Chametz was sent by a Jew who did not perform Mechiras Chametz, then the Chametz is to be destroyed, as explained in Chapter 3 Halacha 14A.
 See Chelkas Yaakov 1:44; Piskeiy Teshuvos 448:32