To Be Part Of A Rebellion, It Helps To Tell People About It

I migrated this mass e-mail list I had onto my Yahoo!  I tried e-mailing everyone about my plans, and after I hit send I got this massive wave of "MAILER-DAEMON" and "returned mail" notices.  I sent it out to, I think, 150 people and I got spammed back on, like, 90 of them.

Is Yahoo! Mail not able to send out the same e-mail to 150 people, or is 60% of my mailing list fake e-mail accounts??