You can resend an email campaign just to those that haven't previously opened the mail. Helpful in giving those people an extra reminder.

1) To resend an email campaign to the segment that hasn't opened an email, click on the button indicated below in the 'Scheduled' tab.

2) Click "Preview" to open the email before sending it.

3) The email will open, and you can adjust it however you like. When you are finished, click "Preview & Send email".