Yes, the system allows you to import subscribers using CSV files and to also export your subscribers also in CSV format. In the 'Subscribers' drop down menu, you will see the option to "Import Subscribers" or to "Export Subscribers". Select which option you would like and follow the on-screen instructions.
To export your subscriber list follow these simple steps:
Select 'Export Subscribers' from the 'Subscriber' menu
Select what mailing list you wish to export and if you want to filter the list at all (perhaps you only want to export all users from a particular domain).
Set up the options on how you wish to have the export file formated
Start the Export.
To import users in to your list follow these simple steps:
Select 'Import Subscribers' from the 'Subscriber' menu
Select what mailing list you wish to import the subscribers to
Match the formating details to that of your import file
Start the Import
Remember that if you are importing users into your database and you have custom fields that you will have to set these fields up before attempting to import data into them.