Hi and thank you for your question.
Just to clarify, who's your email provider, e.g. Gmail, Hotmail, etc.? Are you able to sign in to the account now, or are you locked out?
Please reply at the box below, and then we will continue further.
I see, all right; it does look like your Yahoo account might have gotten compromised somehow, hence these undeliverable emails are being sent on your behalf. Please open up the following link first:
Sign in to your Yahoo account, when prompted.
Next, click Account Security on the left.
Click Change password. Enter and confirm your new password.
Click Continue > Continue to finish.
This should do it. If you need more help, please use the Reply box below to continue our conversation.
Otherwise, kindly take a moment to click (and submit) one of the five star buttons at the top of this page to rate my service. Thank you.