Retired LL's guess:
The police don't make the laws --they may be more interested in keeping the peace.
is a potential problem with the meaning of the word "owner" in NH L-T
laws and I have no clue how it shakes out--I would hope it means a
tenant is the equitable owner of the occupancy rights and has the
appropriate ownership rights....
But anyway , by definition, a person without a lease living in owners home which is owners regular residence is NOT a tenant. See NH--540.1 IX (d)
In short its OK to just boot guests as they are not tenants !
Getting mail there is totally not a relevant point.
But thats not the precise words--ask your attorney first-or boot them and then see it they bother to take it to court and then you defend.
But don't give them any sort of oral or written lease!!!!