It depends on the status of the email. These are the possibilities:
Infomail, Spam, Virus
If the customer uses archiving, these kinds of emails can be redelivered. Status will stay as delivered. The email will be delivered again, and a new entry will show up in the Email Live Tracking. This new entry will have the reason "Statusmail". For customers without archiving a later release of an already delivered email, is not possible.
These emails cannot be released nor redelivered, because they were rejected either from us or from the destination server.