1 of 1 people found this helpful
You probably want to start with clickers and openers, then with people who were delivered the email. The point is that if some opens the email but does not download images, you will never know.
2 of 2 people found this helpful
I have found that it's best to wait and see before pulling the trigger on a retraction email (as long as it wasn't sensitive or timely material). As you said, people may get the retraction and not even realize the first email was in error. My preference is to handle the responses as they come in instead of drawing further attention to your error.
If you are going to do go for a retraction, you could do it in segments (opens/clicks first) and make sure it's from a senior member of your organization.