[nitrogen]

It's still possible to identify where the letter was sent based on the postmark and unique barcode printed on the envelope when it is scanned.

Based on https://news.ycombinator.com/item?id=5986635 and https://news.ycombinator.com/item?id=5986011

Edit: this comment is for scrabble's sake, as you and I already exchanged comments on the subject.