When creating a distribution list in Classic from a query, members who are subscribed to this list are not automatically removed by 'resyncing' the distribution list.
Members can be unsubscribed in two ways:
1. To remove individual members - please see further details here
2. To remove members from the list in bulk, this can be completed via a query. Follow the steps here and instead of subscribing members to a list, you can select to unsubscribe them
Then, sync your distribution list in the Classic console to update Campaign Monitor
An example of removing members in bulk from distribution list:
You may have previously created a list for 'Unfinancial Members', and some time later, you are looking to contact these members again. There may, however be members who have signed up since the last email, therefore you will want to remove them.
To do this, create a query called 'financial members' - or update the query you previously used. Then, when viewing the query, select the distribution list, and 'unsubscribe'.
From here, the last step will be to resync the database to Campaign Monitor which will remove the members that you have just unsubscribed.