tomaildir is a little tool to send a message to a maildir. I use
it in a .forward on a sendmail host.

tomaildir uses qmail compatible exitcodes. See the manualpage for
details.

Use it like this:
	tomaildir [-g greeting] [-i inputfilename] dir
Without the -i option smtpblast will read from stdin. That's the right
behaviour for your .qmail file (where you don't need this, but it's
equally useful with sendmail).
The -g option allows you to override the local hostname (which is used
to make hostnames in the maildir unique. Therefore this option makes it
possible, if used stupidly, to screw things up).