@Thomas3682,
I would check with your city rules on this as it differs from city to city about rules regarding establishing residency, establishing tenant rights (many places allow people to have tenant rights over 28 or 30 days) and then it is harder to evict them and more costly too (if it ever did come to that).
I would reach out to the guest and ask why they are receiving mail there as this is not normal nor did they ask you to do so. I would also reach out to Airbnb support to ask them what they suggest to do in this case as it concerns you, the guest didn’t ask you to do this, etc.
Please let us know what you find out or what happens.