When I sent over 100 emails including one addressed to myself, and two with errors (ie; .com instead of .net, altering the users name, etc.) my email was sent correctly but I got no feedback to my MAILER-DAEMON folder of the fake addresses. I'm using Thunderbird and my email address is sbcglobal.net.
Try checking the spam folders both in the webmail on your ISP webmail (might be provided by Yahoo for your sbcglobal) and in Thunderbird's spam folder.
We're you able to find the bounces in either of those locations?
It's also possible the bounces were not delivered back to your email account.