Creating a list of users to import into

This is in addition to my previous question.
We have an Imail server up and running. We are changing it all over to an exchange 2000 server. All I want to do is make a list of users exported from the IMail Server and easily import them into my exchange sever. I have tried various methods of which none are working at all. Can anyone tell me the
easiest way to to this? Thank you.