External Contacts list in Exchange 2003

Ok so I feel like a bit of a numpty for asking this, but so far all my attempts at working it out myself have proved fruitless.

I had an external contacts list of 4-500 email addresses on my Exchange 5.5 box, which I exported as a .csv file just before I turned it off… The 2 exchange boxes where never in the same domain and thus never saw each other so I couldn’t move it accross as part of an upgrade.

How do I get my external contacts list back into Exchange 2003 from a .csv file extracted from 5.5?

And failing that; how do I actually type them into the system to get them to appear in the external contacts list?

I’m running Exchange 2003 on Windows 2003 servers. I got everything else working fine, but this has beaten me – how stupid do I feel? 😉