Hello Gary,
I have not run in to a limit yet in this area. We have noticed performance issues in the past with huge whitelists, blacklists. We have added optimizations here but you still may see some issues with list that size that will need to be checked on ever incoming connection.
You should be able to paste the entire list in to the text box.
Tony Scholz
System/Network Administrator
SmarterTools Inc.
(877) 357-6278
www.smartertools.com