/var/lib/qmail/rc is in qmail-run 2.0.2+nmu1.
This file is owned by root:root, with mode 0o755.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 | #!/bin/sh
# Using stdout for logging
# Using control/defaultdelivery from qmail-local to deliver messages by default
exec env - PATH="/var/lib/qmail/bin:$PATH" \
qmail-start "`cat /var/lib/qmail/control/defaultdelivery`"
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