There are multiple ways to receive letters. Having a mailman delivering it directly to your house is usually the rich area's way to handle it. The lower version of this is to let people check with the post office themselves. If it's fancy, you have at least your personal postbox there, or you will have to ask office-workers which then depends on their working time. And outside of this, there are other ways to use other locations and people, not directly affiliated with the postal service for delivering letters. Pubs and other shops are often such locations, or in really poor areas the village chief will receive them, and then handle distribution.

But it should be noted, except the physical objects, those letters can be also replaced with other means of communication. Just calling people via phone is common, or nowadays sending an email will also do the job. In my country we have a working and reliable postal system, but companies are still replacing letters with digital communication as far as laws allow it. Payments are also running automatically, so the bills are more informative and for taxes.