DF - this is quite common, as G the W says, and extremely tedious! Someone/several have 'harvested' my wife's email address (from a web site, so our fault!
) and are 'forging' the 'from' address on their spams (easy to do) to look like us, so it bounces back. Now't you can do except change your email address. To 'lighten' your inbox, there are a number of progs which download only the 'headers' in your email and will allow deletion after 'inspection' before you download. I and many use 'Mailwasher' and there are several others.
There are ways to 'read' the email header (
http://www.pprune.org/forums/showthread.php?t=249084 post#3) and seeing true origin but the chances getting it stopped this way are minimal.