May 19, 2015 — By WSU News Services — A postage rate increase will become effective Sunday, May 31. Rates will increase for certified mail, return receipts, registered mail, media mail and library mail. The extra ounce rate for letters and flats will increase from 21 cents to 22 cents. International 1 ounce letter and postcard will increase form $1.15 to $1.20. International express and priority mail will also increase with this chang