You can select “is not a member” when using list filters. So if you already have a list that has your members, or customers, or similar. You would simply choose list membership as a filter option, and instead of “is a member” select “is not a member”.
Alternatively you could also simple exclude your existing list of members, customers, (any orher predefined list) in the “do not send” option when sending an email.
Aah thankyou - rookie error, I was focussing so much on the first column and trying to find the negative in the initial list that I didn’t notice a dropdown option had appeared in the second column once the property had been selected.
You’re right, not all filter options in lists are available as their negative version. Some are (“contains any of” vs “doesn’t contain any of”), but not all.
Whenever that is the case, you might have to create a second list, like @franksteiner79 explained, and then use the list membership filter to exclude those contacts.
For example, you want a list of contacts which are not associated to any won deals. It’s easist to first create a list of contacts which are associated to won deals – then create a second list of contacts which are not in the first list.