@Josephine70 just a couple of things to check before answering : can you tell who the sender of the mail is? Is it a credit card statement or from another lender?
I ask because you may find the guest has used your address to commit fraud, so if it’s lender mail then I would contact them directly and let them know. I had this happen to me at a previous property and it turned out a woman had used my address to clock up over $15,000 in debts to various places. It then began showing up on my credit rating, as a “known person of poor credit” was tagged as living with me at my address. I had to get onto this quickly and once I did, it was easily solved.
If it’s just standard mail then I’d say you’re safe to return to sender.