If a client unsubscribes and then entered back on a contact import, will the system know not to add them back in?

If a client unsubscribed and is re-uploaded, AdvisorStream will remember their preference status. The contact will remain as an unsubscribed contact even if you import them back to your contact list. When you send out your newsletter, AdvisorStream will ignore the unsubscribed contacts, and will not deliver to them.