It sounds like your list is not correctly formatted, is there a yellow triangle with an exclamation mark next to your list? Click it to get the error log for your list.
A CSV formatted file should look something like this (See Developers Guide for EPiServer Mail for more information):
The import is not scheduled; it is done in a background thread.
When trying to import large csv files with recipients I get this message
The recipient list has been uploaded and the import process has started. Please wait until the import is finished and the recipient list appears under 'Recipients'.
I have waited and nothing happens. If I reload the page I get the list but with no recipients. Is the import job based on some scheduled task or how does that work? Can the job somehow be monitored or triggered?