If the other fields are accurate, the post office will get it there.
When I lived in Evanston, Ill., a friend send a letter to Analville, Ill. with the correct ZIP Code. It got to me.
One time I gave a salesperson a bogus address (1234 Main St.) because I didn't want to be hassled. I did give him the correct company name. (It was printed on my conference badge, so I couldn't lie about that.) It got to me.
I've sent letters with the wrong ZIP Code and incorrect city and it got to the correct destination.
If someone has a P.O. Box and you use just the ZIP+4 as the address, it should get to them.