To Tom_in_CA: that's EXACTLY what an early post office was, especially in the 1800's. A localized place where multiple people could all get the mail from the same back porch (sometimes front porch) instead of going into town and getting it. Often just small communities that let you know there were several families living nearby. Usually had what we would call a convenience store as well. At least that's how it usually worked here in OR.
Point is that's where the local people would walk to or ride to for their mail at least once a week. Trips to town that could take a full day were reserved for larger buying sprees. And most small farmers made their own food: wheat, oats, barley, eggs, milk, cream, chickens, cattle, sheep, etc.
For 4 years I went to grade school in one of those locations: Plainview, OR. The ultimate in small towns. Everyone knew everyone else's business, relatives, and personal attachments/affairs. It was either real cozy or real nosey, depending on how you viewed it. My dad used to walk to the same school when he was young: 5 miles cross-country one-way. Since there were lots of pheasants around then (the first Chinese Ring-Necked pheasants were successfully released in the US from Judge Denney probably in an old fruit orchard nearby) he would take a shotgun to and from school to back some fresh fowl for making pocket change during the Depression. Today he'd be jailed for bringing a firearm to school! But in the Depression that was called being a good shot and a good way to make some spending money.