Though I have no experience with L-Soft's other products, you might consider these thoughts:
1) the db should be able to feed you a job of incremental changes (add, remove, updates (name and/or userid))
or
2) a flat-file (of all target userids) should be able to be produced for each (what might be infrequent) mailing -- that could be input to a LISTSERV Distribute MAIL job
/Pete