workflow for bounced email gets triggered, but email is status = opened

workflow for bounced email gets triggered, but email is status = opened

Hello,

I have a workflow that sends me an email if outgoing email are bounced.
Now I got some kind of this emails, but the corrosponding contacts have status = open at the email.
Why this bounce-workflow is triggered?

Reports > Email Reports > Bounce Report is empty.

Thanks & Greets