Thanks for the reply, ozmarks.

As mentioned by Adrian_A, we can view the delivery errors from the Tasks section.

1. Go to the Dashboard menu.
2. Under Tasks, select View the errors.

The View the errors link lists the emails with delivery errors sent through your email provider's server. You can see the delivery date, type, Ref No., Customer, error, and delivery method in the delivery errors section.

If you're unable to find it, you can reach out to our Customer Support Team so they can further check it. The new "Help" menu interface: 

1. Click the (?) Help icon and choose the Talk to a human option (then type it again when prompted).
2. When asked by the bot, type "Bounced emails."
3. Select I still need a human, then proceed with Contact us.
4. Tap Let’s talk then choose either Get a call or Start messaging. 

For the old "Help" menu:

1. Click the Help icon, then the Contact Us button.
2. Type "Bounced emails​​​​​​​​​​​​​​" in the What can we help you with box.
3. Proceed with the Let's talk button.
4. Select either Start messaging or Get a call button.

Keep on posting here if you need anything else. Stay safe!