Former mail carrier here would get several pieces of a neighbor's mail in our mailbox each few weeks. No similarities in the names at all, so all we could figure is that the sorting area at the post office has this neighbor's sort box just above or below ours. We put the mail back in the box, flag up, and it would be straightened out the next day. That carrier went to another route, the guy we have now hasn't had that issue yet. 

B-i-l is mail carrier in Amish territory. Where there are three each Eli Millers, Jonas Yoders, Ezekiel Borntragers, etc, etc etc up and down the roads. I've never understood how he keeps 'em all straight. And he says most of them get pouty if they get someone else's mail or someone else gets theirs. I don't envy that job.