mailshot

noun

a circular, leaflet, or other advertising material sent by post, or the posting of such material to a large group of people at one time

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012