In email insights, if you select a database with an associated seed list and choose to run a spam test, emails will be sent to seed list recipients. It will not send this message to the contacts in this database.
By default, Acoustic Campaign includes your seed list recipients on any email sent. If you don't want email insights to send the message to those recipients, you either need to remove the seed list associated with your database or create a test database without a seed list.
Note: For email insights to test the spam scores for each spam filter, a "live" mailing has to be sent so it can be monitored. Also, only Email Keyed and Non-Keyed databases work for previews with spam tests. If you select a database that has a unique identifier other than email or it has multiple unique identifiers, you receive an error message and previews won't generate.