I setted up a test account as "host" Mailbox with the same setting as
my office mailbox and tested imap on the commandline as you said.
You will find strace the output on the bottom.
There is one curious line:
access("shared-folders/test/allgemein/shared/cur", W_OK) = -1 EACCES
I also tried to set up a read-only shared folder. I noticed that only
messages in cur/ are visible to the subscribing user, while those in
new/ are not. syslog says that the rename from new/ to cur/ was denied.
I suppose this is the line above, isn't it?
When there is p.ex. one message in cur/ and another one in new/, a raw
IMAP session shows that there are two messages existing, where one is a
recent one. Fetching the contents of the recent one fails.
To make messages from new/ available to all users, they must be given
write access to cur/, new/ and tmp/ (I checked all combinations). This,
of course, allows them to delete arbitrary messages, sapping the
I consider this a bug, isn't it? -- Where are bugs to be reported?