I always use the exact format that USPS suggests, but I actually had a vendor change it to not include the +4 after the zip. Was this coincidence, a mistake, or them actually knowing something that I don't?For example (obviously this is made up, but I may as well point out it's fake, ahem):JOHNATHAN SWIFT122 E TOWER RDMIDDLETOWN CT 10054-8343All caps, no period for abbreviations, and all abbreviated where common (road should be RD, etc.) I thought it was best that way, since it should blend in perfectly with business mail and whatnot. But I suppose it's possible that if the sender doesn't also use the full zip+4, it might look weird?