You can still use the .csv files from the Exchange Server 4.0 CD for exporting and importing in Exchange Server 5.0 or 5.5. If you do not have the Exchange 4.0 CD, the sample CSVs are located in the following file that can be downloaded from the Microsoft Download Center:
Release Date: 09/11/98
For more information about downloading files from the Microsoft Download Center, please see the following article in the Microsoft Knowledge Base:
119591�
How to Obtain Microsoft Support Files from Online Services
If you are unable to download or locate the .csv files, the Header.exe utility from the BackOffice Resource Kit can be used instead to create a .csv file with only the required headers for importing.