A few days ago I had a scam email, a bill, which I had nothing to do with. I deleted the email and at once I had a huge list of undelivered emails from my account to people I didn't recognize. Since then there are a number of my email addressees who cannot receive my emails - they come back undelivered. Has anyone had this problem? And how can I put it right?
Which email provider do you use?
Have you changed your password?
Look at the email header of one of the returned emails you refer to on line 2 of your OP. What is the email address of the original sender? Is it identical in every way to your email address?