Thank you Anurag - I get how to create a list of people by using that filter, but I do I exclude them? I want to email this group of people, but not this group. Can you please tell me the exact filter to use?
I'm assuming you're using a smart campaign to send out the emails?
Step one: create a smart list with the filter i mentioned above. This will contain ONLY the attendees of the original webinar
step two: In the smart campaign that you will be using to send out the invitation for the encore webinar, you can use the filter "member of smart list" NOT IN ... the smartlist you created.