You may have need for QS to prepare mixmaster message(s) for you--but not actually send them. Off hand, I can't think of a reason, but this feature was requested and used by some in earlier QS.
To save messages to a directory rather than sending via SMTP, just put the directory name in the QS Host header. Here's an example:
Host: c:\qs\messages
QS will name messages, message1.txt, message2.txt, etc. If there are already messages in the target directory, QS will use the first unused name available. For example, if the directory contains message1.txt and message2.txt, QS will name the message message3.txt. For another example, the directory contains message1.txt and message3.txt. If QS saves two messages to the directory the first will be, message2.txt and the second message4.txt. If you open the directory and are uncertain as to which messages are the new ones, check the date and times of the files. Of course, this all becomes academic if you simply delete messages from the directory as you use them.
IMPORTANT: THE DIRECTORY MUST EXIST! That is how QS decides you want to send the message(s) to a directory. If it doesn't exist, it just becomes an invalid host to QS.