It is an error to set up a black-box-directory without a directory for each user under it. The software will NOT run under such circumstances. In versions prior to imap-2002, it will segfault due to a null pointer. In imap- 2002, it will issue an error message and crash.
There is an additional, undocumented, /etc/c-client.cf command which can be used to set up a default directory. Usage of /etc/c-client.cf outside of UW is not supported, and the documentation goes to great lengths to discourage use of it. That is why you are required to enter "I accept the risk" into /etc/c-client.cf. Think of /etc/c-client.cf as being like the Windows Registry; you can do a lot of powerful things with it, but you can also cause catastropic failures. Black box mode is not supported outside of UW either. We don't use black box on our main IMAP servers, just on a few internal support systems. Black box was an idea that we have largely abandoned in favor of better mechanisms. It is likely that the code for black box mode will be removed entirely in a future version. I strongly encourage you *not* to use black box mode. Even after you get it configured correctly, it probably will not do what you want. Instead, read the imap-????/docs/CONFIG file to find out how to configure the software to do what you want.
