Go to Reporting > Customer Management and scroll down to Email events, filter the Email status to bounced and it will show you which email address, what exactly bounced and why.
You can also search by a specific Email address or Invoice Number
Go to Reporting > Customer Management and scroll down to Email events, filter the Email status to bounced and it will show you which email address, what exactly bounced and why.
You can also search by a specific Email address or Invoice Number