My target is 40 million separate messages per day with a standard IDE disk. The standard BIND resolver library accounts for a huge chunk of the space taken by each qmail-remote process. A future version of qmail will support an alternate, much smaller DNS library that talks to a nameserver on the same host. My new dynasub package will accept subscription requests from local users and negotiate subscriptions with remote mailing lists. It will automatically set up a local sublist for each remote list, to speed delivery and protect user privacy.
Clients run mini-qmail to pass all mail to a central server.
The qmailanalog tools no longer require that you keep qmail's entire log. They store crucial information in a table on disk.