iMS 5.2 and earlier are not supported on W2K.
As far as distribution lists go, are the recipients users hosted by iMS or are they elsewhere? For users hosted by iMS, you can see Chapter 5 of the Provisioning Guide and use LDAP. For list containing random users on or off your system, you could use the aliases file, no API is provided, and obviously the aliases file can only be edited by the system admin at the UNIX prompt. For more information on the aliases file, see Chapter 6 of the Admin Guide.