Attached picture is a screenshot of my blocks. As you can see here the list has 2 items having email addresses in it. You can check the below Do It Result. Also, you can see the text input which contains the same email address. So why the “is in list” block returning false?
What you should have done here is to use add item to list block once airtable got value. It will work that way. The value gotten will be added to the created list, then from there you can check if it’s in the list of values.