Rapid Email Sender saves all campaign data in its own database. You can easily get all undelivered recipient mail. Here are the steps:
1. Press Mail Data>Mail Sending History
2. You will get a list of all sent email campaigns.
3. Select the desired email campaign.
4. From toolbar menu press Export>Export Undelivered
5. Browse a location in your computer and enter a name to save all undelivered mail from selected campaign.