Problems with newsletter

Hi!

I have a little problem with sending a newsletter to my members. I can send it without problems and most of my members recieve it in a very short time, but there are a few which do not. I've set the newsletters so I also get a copy on my e-mail and after a day or more I get an e-mail from Mail Delivery (MAILER-DAEMON@forumotion.com) stating that one or more members couldn't recieve my mail. Is this because they have registrated with a wrong e-mail adress, an e-mail adress which does not exist?

Thanks!

i think it wrong email address and does not exist