Tinymail can't create folders on my IMAP server

[Armin Burgmeier <armin arbur net>]

I cannot create new folders with tinymail on the arbur.net IMAP server
(it is a shared one, so I don't have direct access to it, but I can
probably find out some more information if required), though it works on
the openismus.com one. I figured out that if I replace "/" by NULL in
the call to camel_store_create_folder() in
tny_camel_store_account_create_folder_default() at line 856 of
tny-camel-store-account.c,

info = camel_store_create_folder (store, NULL /* "/" */, name, &ex);

creating folders works on both accounts (as it works with evolution,
btw). However, I am not sure what the "right way" is neither am I sure
whether it breaks folder creation on yet another server. Is there a
special reason why "/" is used as parent folder instead of NULL?

Thanks,
Armin