After looking at the way Maildir represents subfolders, I changed the sieve line from
fileinto "Lists/NCCC";
to
fileinto "Lists.NCCC";
and now it files into the NCCC subfolder of Lists as I wanted. I'm not sure whether this is the expected behavior or just an accident that plugging that string into the file name happens to result in the right name.
I haven't tried, but if it's just passing the fileinto argument along with minimal inspection, I'm afraid the answer might be use "Lists/NCCC" if mail is in mbox format but "Lists.NCCC" if mail is in Maildirs, and it certainly seems that users editing their sieve scripts shouldn't have to know that.
Rich
dovecot -n shows:
# 1.0.10: /etc/dovecot/dovecot.conf log_timestamp: %Y-%m-%d %H:%M:%S login_dir: /var/run/dovecot/login login_executable: /usr/lib/dovecot/imap-login mail_privileged_group: mail mail_location: maildir:/arda/export/mail/%u/Maildir auth default: passdb: driver: pam userdb: driver: passwd