Do you black list email addresses that are bouncing emails?

I have a client not getting their email notifications.

We do indeed block addresses that reject emails.  If you believe and address is on our bounce list, you can remove it from your end:

https://www.jotform.com/help/262-How-to-Remove-Your-Email-Address-from-Bounce-List

You can check your email logs to see if the emails have been failing:

https://www.jotform.com/answers/594650-Viewing-email-receipts-or-email-logs

I checked our logs for the addresses in your most recent form and it looks like you have already taken the address off our bounce list.  If you have any further questions, let us know and we will be happy to help.