The List Acquisition and Refresh setting in Blackbaud NetCommunity Configuration only defines the time at which Blackbaud NetCommunity will refresh any lists that have been manually queued for refreshing.  A list is manually queued by editing the list and clicking the Refresh List button.

Lists are automatically refreshed each time an email message is sent to the list.  It is not necessary to manually refresh a list before sending a message to it, as such.
Note: This will not update the list refresh date as the message itself will pull the data directly from Raiser's Edge unless the list is a CSV file or based on a static RE query.