That's right, the logs show the program name (smtp) not the transport name; you can't tell which transport called smtp.You can add something like -o syslog_name=postfix-slow to the master.cf slow transport entry to differentiate the logging.
That's it. Postfix is awesome and very well designed. Such kind of change would need 723435 patches in qmail (and that's why I'm migrating all my qmail servers to postfix).
Thanks a lot. -- Santiago Romero
