We have approximately a dozen lists with subscriber counts in excess of 5,000,
including three lists with subscribers counts of 10,000 - 16,000, and we are
not experiencing problems related to the number of subscribers.

I think the performance issue on very large lists involves list updates (bulk
add and bulk delete jobs) with large numbers of subscribers. If you read the
L-Soft literature about LISTSERV HPO (High Performance Option), it seems to
indicate that the performance benefits are in the area of list updates.

--
Paul Russell
Senior Systems Administrator
University of Notre Dame