It's a patch to qmail-1.03-qmtpc to allow artificial QMTP routes.
To use it, you must first apply Russell Nelson's patch to the qmail source tree. It enables QMTP deliveries in qmail-remote, on the basis of MX priority.
Then, apply this qmtproutes patch.
The file control/qmtproutes in the qmail directory has the same format as control/smtproutes. When qmail-remote sees the recipient domain listed in control/qmtproutes, it will artificially send the mail to the associated host, with QMTP ; it will fall back on SMTP if that doesn't work. Be aware that the use of qmtproutes bypasses any MX field in the DNS.
This is useful when you want to send all your mail to a smarthost via QMTP, and you don't want to bother setting up an ad hoc DNS configuration, which often implies split-horizon and other miscellaneous pains.
If the recipient domain is listed neither in control/qmtproutes nor in control/smtproutes, qmail-remote will choose the protocol according to MX priority.