what is the smallest envelope you can mail
Last Updated: Feb 20, 2014 03:17PM EST. According to the USPS, the smallest mailable envelope must have the following dimensions: 3 1/2 inches x 5 inches. Please click the following links to learn more. http://pe.usps.com/businessmail101/mailcharacteristics/letters.htm http://pe.usps.com/cpim/ftp/manuals/qsg300/Q201.pdf. Yes I found this article helpful.