All of a sudden, all email to this mailbox has started bouncing.
The .qmail-default file for that domain is missing.
Re-create it with qmailadmin by setting a bounce option for the domain, or by doing this (all on one line, as user vpopmail, or just fix the ownership after you do it):
echo "|/home/vpopmail/bin/vdelivermail '' bounce-no-mailbox" > /home/vpopmail/domains/bitblit.net/.qmail-default
-- Tom Collins [EMAIL PROTECTED] http://sniffter.com/ - info on the Sniffter hand-held Network Tester