Data Overload

Ok... if you have read my last posts you will know i am trying to sort a few users... well, I found out today that PHP can only handle so many things at once... See, I have this file: http://www.nozonenet.com/users.txt and I need to sort all of those users into different files, according to there domains (after the @ but before the tab)... only problem is that PHP can not handle that big of a file, at least I can't make it work with it... can someone please give me a idea on how to write this.. like a framework or something.. I am on a schedule and this is bugging me like heck... (our server just got hacked, and I need to insert all of these users back into the server, if I did it like it is now I would be working for weeks)... Please Help!!