Well, for square letters that is.
On May 12, the same day as postage going up for standard sized envelopes, the cost of a square First-Class letter or card up to 1 ounce in weight increases to 62¢.
Why? Well, square envelopes require special handling.
The Postal Service has become highly automated, using machines to help sort the mail. Square envelopes will not feed automatically through this equipment so have to be sorted by hand. They call these pieces non-machinable and attach a surcharge to offset the additional cost of sorting and processing these pieces of mail.
Along with square pieces, anything that has a button or clasp on it, or something stuffed inside that makes the piece uneven will require 62¢ in stamps as well because it cannot go through the automated equipment.
Square letters are fun to send and receive, even if they do require a bit more postage. They call attention to themselves by saying, “Look at me, I’m special. I’m not junk mail. I was sent by someone willing to put some extra thought and cost into sending you something extra special.” So, think square, think 62¢, and do think to send something special to a friend!