Still no dice, I tried every variation I could think of, and it's still trying to interpret the executable command as a literal string.
I have this working on another server. However, I'm in the middle of a migration to a newer machine and wanted virtual users/domains as described in the tutorial linked above (the older machine is sans those features).
I've tried adding a transport to local delivery, as well as maildrop, and still nothing.
For context, I'm trying to get SmartList http://www.animalgenome.org/SmartList/