Keep Mail Safe Act This bill directs the U.S. Postal Service to report to Congress on retrofitting mail collection boxes to prevent mail theft. The report shall include (1) a strategic plan to retrofit all mail collection boxes with narrow mail slots; (2) a statement of the resources necessary to carry out such plan; and (3) with respect to any mail collection boxes that have been retrofitted on the date of enactment of this bill, information on their locations, the security enhancements made, and the reasons for their retrofitting.