[Kolab-devel] IMAP and "flat" namespaces

[Bernhard Reiter]

Hi Kolab-Developers and Friends,

over the years I've often heard the question about "INBOX" being displayed in 
a Kolab Client and all folder being subfolders to it. I've just published a 
small result of this consideration to:
https://wald.intevation.org/plugins/scmsvn/viewcvs.php/trunk/research/imap-flacher-namensraum-de.txt?rev=2&root=kolab&view=log

Attention, this document is in Germany.
The short summary:

To use a "flat privat namespace", which means having folder belonging to one 
user in parallel to the special IMAP folder "INBOX" is okay with the IMAP 
standard RFCs.

There is one conceptual problem, that is irrelevant in practice, if you intend 
to add more non-private namespaces later in an IMAP  installation.

For the implementation side there are some more remarks:
a) Clients must be able to clearly detect if a folder belongs to other users 
or not, so an empty private namespace must not be checked against the folder 
paths first or this will fail.
b) Servers should block the creating of private folders having names that are 
to be used by other namespaces, e.g. "user/".
c) Clients can implement to display folders being parallel to the special 
folder "INBOX" independently which model is used by the server. 

It would have been cool if the IMAP specs would disallow the use of the 
empty "flat" private namespace, which would implementors live easier for 
clients and servers. 

Currently a cool IMAP Client must implement both schemes reasonably well.
Given the Cryus IMAPD by default supports the "private INBOX namespace",
and it is easier to implement on client side, I suggest that our default 
configuration for IMAP servers with Kolab should be to use the "privat INBOX 
namespace"  and improve our clients to display that nicely.

Bernhard
-- 
Managing Director - Owner: www.intevation.net       (Free Software Company)
Germany Coordinator: fsfeurope.org. Coordinator: www.Kolab-Konsortium.com.
Intevation GmbH, Osnabrück, DE; Amtsgericht Osnabrück, HRB 18998
Geschäftsführer Frank Koormann, Bernhard Reiter, Dr. Jan-Oliver Wagner
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