It's not a configuration problem (unfortunately)
To irmongoose: I do not switch from Windows, but from some other Unix.
You are right, if I were switching from Windows, I could live with the
problem (Outlook is not a very good IMAP client...)
Thanks for the offer for help dricci, but it is not a configuration
problem.
You are right, IMAP is a standard, but Apple does not have a very
good reputation as an IMAP implementor. E.g. in 2001, there were
some discussions about the fact that Apple developers just missed the
possibility that an IMAP server uses another hierarchy separator then
the slash. The Cyrus IMAP server uses a dot.
Here is what Mail.app does (derived partly from network level traces of
the IMAP communication between Mail.app and the server).
The good news is that Mail.app handles the IMAP protocol correctly. After
logging in (and I appreciate that Jaguar added some new authentication
mechanisms, including Kerberos), Mail.app retrieves a list of all
folders from the server. These folders are then available to rules
(incoming messages can be moved automatically to the folders) or to the
menu option that allows to move a selected message to some folder.
The problem is that the Cyrus IMAP server places all user folders as
subfolders of the INBOX (just as all user directories in a file system are
usually subfolders of the home directory). In 10.1, Mail.app displayed
a small triangle in front of the INBOX icon, clicking on the triangle
revealed the subfolders. The user interface embellishments in 10.2 made
the triangle disappear, so subfolders are no longer accessible.
For a UW IMAP server, this is not a problem. That server places user
folders on the top level, they will show up in the folder tray. It is
also not possible to have messages and folders in a UW IMAP server,
so for the UW IMAP server, the INBOX cannot have subfolders, so the
INBOX folder does not need that little triangle. I conjecture that
Apple developers only test with the UW IMAP server (UW IMAP also uses
the slash as hierarchy separator, see above).
It is possible to make the folders visible on the top level: if you set
the prefix in preferences to INBOX or user.uid, the user folders are
now at the top level (just below the prefix, that is), so the show up.
Unfortunately, this makes the INBOX unaccessible, because Mail.app now
refers to it as INBOX.INBOX. Here is another problem with the prefix
in Mail.app: real IMAP servers have at least two name spaces: one for
user messages, and one for shared folders. Mail.app would really need
to prefixes: one for user folders (not to be applied to the INBOX,
is they do now) and one for shared folders.
I sent a bug report to Apple about the problem in october, and had
hoped that it would be fixed by 10.2.3. Mail really is important for
me. I handle over 1000 messages from customers and partners every month,
this is just impossible without folders. And please don't recommend other
mailers: I don't want to create a dependency between such a basic function
and the OS. Mozilla just cannot handle Sent-folders correctly (this is
a legacy from Netscape 4 days). Entourage? Well, M$ is not an option.
If the powerbook came with 10.1, I could survive some time. But this means
no updates, no SuperDrive. It also means a used system, not a new one.