Happen six days a week,when the postal carrier enters on property boundaries,and sometimes even breaches the perimeter by sliding envelopes inside the home.

Some cities also have sales papers and coupons placed onto porch regularly,usually they are delivered by a different stranger,every day.

To perform a variation of this,changing it to personal protection(in dogs mind)...as the strangers make their rounds,stand in yard or near front gate of property with dog,while waiting for him to (momentarily)trespass.