Hey @Hanspeter
Thank you so much for coming to the Klaviyo Community for help with your bounced emails.
How you handle resending a campaign will depend on whether or not these were Hard or Soft bounces. If they are hard bounces you will not want to resend this campaign to them as it can negatively impact your deliverability. If they are soft bounces because either their inbox was full or there was an issue with the server at the time of send, you can resend one at at time by going into their profile or from the Recipient Activity view of a message. The link I included previously will walk you through how to resend the emails to your customers. Keep in mind that the best way to reduce your bounce rate is to complete a list cleaning. This article will tell you how to clean your lists and maintain strong deliverability by identifying and suppressing unengaged profiles. Cleaning unengaged or inactive profiles from your list improves a number of aspects about the quality of your list. This is crucial to maintaining good deliverability.
Hope this helps get you back on track! Thank you so much for being part of the Klaviyo Community!