Function: Inserts a new subscriber into the database

Function: Adds subscriber meta field for a subscriber.

Function: Empties the subscriber cache.

Function: Marks a subscriber as confirmed (Double Opt-in)

Function: De-activates a Noptin subscriber

Function: Deletes a subscriber

Function: Deletes a subscriber meta field for the given subscriber ID.

Function: Checks whether a subscriber clicked on a link in a given campaign

Function: Checks whether a subscriber opened a given campaign