I have 20 email addresses that bounced.  Most of these - although listed in the bounced category - came with the message "user unknown" or similar.  I subsequently found new email addresses for some of these folks and tried to put the new emails in place of the old "bad' emails that were listed as bounced.  I have tried to re-email these people with new email addresses and I can not.  What do I have to do to email these people?

The "bad email" is not checked.  These people have not unsubscribed as they have not received any emails yet - they are all still prospects. 

Thanks.