Yes. The letter will still be delivered as long as the address is correct and there is a stamp.
What we found is that all package services, periodicals and standard mail “flats” that you plan to mail using automation, presorted or carrier route rate, labels must be in the top, and they must be sideways or readable from the top edge. The address labels cannot be upside-down with respect to the top edge.
USPS is using automated systems for sorting flat mail as part of its Flat Sequencing Strategy. This equipment sorts the mail in sequence for mail carriers, which should reduce the amount of time they need to spend on sorting. In order to work in these sorters, periodical addresses need to be machine-readable.
The USPS may charge you additional postage or have you correct your mail.
Snail mail is becoming less popular every single year due to slow delivery times, but some tips for sending things snail mail can still make it a reliable option if you can’t afford other options.