When people email me it bounced back and they get Delivery Status Notification (Failure)

I have only been getting a few emails per day the past week. Then, family member said she tried to email me and it didn't go through.
Another friend emailed me and got a message that says "delivery status notification (failure) from *** Email address is removed for privacy ***.
"This is an automatically generated delivery status notification delivery to the following recipents failed *** Email address is removed for privacy ***."
I tried to email myself with test and subject line and never got it.
In other words, my email doesn't work anymore.  People can't email me when they do it bounces back and I'm not getting all my email.