[Imap-protocol] Namespace separators

Timo Sirainen tss at iki.fi
Wed Jun 27 10:45:01 PDT 2007

On Wed, 2007-06-27 at 09:31 -0700, Mark Crispin wrote:

> Here's what you really missed, if the client does not implement NAMESPACE,

> the same thing happens: you have a server which, for no apparent reason,

> changes hierarchy semantics in a non-deterministic fashion!

OK, I guess that makes some sense then if the client allows user to
request listing mailboxes under some name instead of finding them out

> >> Does your server list all other users' mailboxes with that command (since

> >> after all a user may have a public access mailbox)? Why not?

> > I was actually going to make it do that, once support for shared

> > mailboxes is finished.


> Any server that automatically lists all other users' mailboxes by default

> has huge privacy problem.

Not by default. I meant it lists all mailboxes where the mailbox owner
has given permission with ACLs (so filesystem permissions won't be

> > I've understood that many commonly used clients ignore namespaces and

> > only show what is visible with LIST "" %, so I'd want to keep it

> > possible to list contents of all namespaces with it.


> I am trying to tell you that that is NOT a very good idea; and this is

> from real-world experience.


> If you do this, you are going to have a huge set of mailboxes listed, and

> many users will react with "what is all this junk in my account, I need to

> delete it."

I guess this all depends on what kinds of namespaces you have. Having a #news. namespace listed using LIST is bad, but I think having "shared mailboxes" namespace visible with LIST isn't.

Actually it looks like Cyrus is doing exactly what I was going to:

1 namespace
* NAMESPACE (("" "/")) (("Other Users/" "/")) (("Shared Folders/" "/"))
1 OK Completed
2 list "" *
* LIST (\Noinferiors) "/" "INBOX"
* LIST (\HasNoChildren) "/" "Other Users/foo/support"
2 OK Completed (0.000 secs 10 calls)

There you have a LIST that lists multiple namespaces. Do you consider
this bad as well?

> This happens with stupid clients that implement NAMESPACE and then proceed

> to list all of those. The user complaints are continuous and regular:

> they want to know how to delete these junk names from their account.

I've actually no idea how I would implement NAMESPACE support for
clients in a way you consider good.
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