hide/disable non-Mail folders in imap-clients?

[hede]

Am Thu, 27 Feb 2014 11:10:26 -0500 schrieb Erik M Jacobs <erik at jumpshipservices.co>:

> On 02/27/2014 03:23 AM, Jan Hofmann wrote:
> > hi,
> > 
> > is there any way to hide or disable the non-mail folders, like
> > Configuration, Calender, Contacts, from beeing published through imap?
> > None of my users uses a real kolab-Client, they all use Imap and
> > CalDAV/CardDAV.
> > 
> > Yes, unsubscribe from them in their mail clients would be possible for
> > some (for some not: Apple Mail can only subscribe and unsubscribe for
> > public/shared folders), but most of them are not-so-technical-people
> > (family e.g.)
> > 
> > Is this possible in Kolab?
> > 
> 
> The issue here is that those folders are doing the "right" thing, and
> are also required for Roundcube to work properly.  The mail client is
> doing the "wrong" thing, because it doesn't implement the IMAP RFC
> correctly / at all.  There's an open bug, for example, on Thunderbird
> for this.
>
> As others have suggested, unsubscribing from those folders in your mail
> client is the "correct" thing to do.  But, really, the mail client is
> broken.

On which IMAP RFC and which point in it are you referring to? And which 
mail client is doing it wrong? Roundcube, kmail or the others?

Mail clients are showing folders which are active (subscribed to) 
and hiding those without subscription. This seems correct to me.

The problem is, if you unsubscribe to a calendar folder in a mail 
client to hide it from the mailbox folder view, it also gets removed 
from the calendar view in roundcube. In reverse, if you subscribe to
a calendar folder in roundcube, to use it as a calendar, it also gets
added to plain mail clients as a mail folder. This is correct behaviour!

Those simple mail clients behave correct if they show subscribed folders,
even if those are no mail folders. That's because in RFC 3501, IMAP4rev1,
_the_ imap reference, there is no such thing like annotations or metadata.

There is nothing like:
A0006 GETANNOTATION "*" ("/vendor/kolab/folder-type") ("value.shared")

But roundcube (and kolab at all) relies heavily on those metadata. 
Even worse: Since 2009 there is indeed an official IMAP METADATA extension
(RFC5464) but kolab still uses (by default) the older IMAP ANNOTATEMORE draft.

So I think there is no "wrong thing" in those ordinary mail clients.
They are simply (partly) incompatible with those proprietary imap extensions 
which kolab is using. Yes, it's called a proprietary extension if it's not 
officially standardised, like it is with ANNOTATEMORE. 

So instead of implementing ANNOTATEMORE in those mail clients I would recommend
using METADATA (RFC 5464) in both: kolab, roundcube and those other mail clients.
(AFAIK kolab can use METADATA if the imap server supports it)

btw: dovecot supports both, the older "imap-annotatemore" (especially for kolab) 
and "imap-metadata" for the newer RFC 5464. Cyrus 2.5, which is yet to be released,
will also bring METADATA and drop ANNOTATEMORE.

disclaimer: these are just my 2¢. I didn't knew a thing about it an hour ago and did 
some research on it in the last minutes... so tell me if I'm wrong.

regards
hede