Sending DocuSign envelopes from Salesforce using the DocuSign Salesforce integration.

One of the recipient email addresses is no longer valid (inactive/incorrect email). The envelope status in Salesforce changes to "Sent", but DocuSign later fails for that recipient because the email address is invalid.

Because Salesforce already marks the process as sent, we are unable to stop or handle  business process correctly.

We want to know:

1. How can we capture recipient email bounce/invalid recipient errors from DocuSign?
2. Is there a webhook or DocuSign Connect event available for invalid recipient/email delivery failure?
3. How can we send this failure information back to Salesforce automatically?
4. What is the best practice to update Salesforce records when a recipient email becomes invalid after envelope sending?
5. Has anyone implemented Apex REST + DocuSign Connect webhook for recipient delivery failures?