I would expect that the dovecot reads the pw_dir from the vpopmail db
instead of using this line
mail_location = maildir:/home/vpopmail/domains/%d/%n/Maildir
which not contains the 0/ subdir. Is there a way to inhibit vpopmail
from storing user Maildir in the subdirs?
You are correct that you should use pw_dir. In Dovecot pw_dir is equal
to %h, so the correct usage is mail_location = maildir:%h/Maildir
To disable the hashing of the user subdirs you can use the compile flag
--disable-users-big-dir but you don't want to do this unless you know
you will never have a large user base.