Patrick O'Callaghan writes:
On Sun, 2013-01-20 at 14:38 +0000, g wrote: > On 01/18/2013 09:15 PM, Reindl Harald wrote: > > > >> which tree structure is reflected to the other? > > > > uhm? > > > > the whole structure is on the server as also the mails > > there is no "the other" at all > > in other words, email client reflects what is on server and email > client user does not have to build structure in client? By default no. The client can of course have its own folder structure, but the two are entirely independent. Many clients also allow caching of server folders locally (usually on a per-folder basis).
IMAP is schizophrenic. On one hand, it's general design seems to be oriented towards letting clients cache server mail content.
But on the other hand, IMAP does several things that make reliable caching of mail content pretty much impossible. This is why, in general, IMAP clients over the years have been crap.
IMAP IDLE has been mentioned here. IDLE is a piggy-back extension. It's not part of the base protocol. Clients cannot assume the server supports it. Therefore, IMAP clients have to support the case of IDLE not being available, and there are servers that do not implement it.
Here's the problem. Not just with IMAP, but with any other kind of a client/server protocol with optional bits that are glued on as an afterthought. It takes a certain amount of effort to implement anything. Therefore, faced with the option of implementing and supporting just the base minimum, versus the base minimum and some optional bits, and then having the overhead of supporting multiple ways of accomplishing the same task, in perpetuity, you can pretty much draw your own conclusion as to how this is going to play out in the long run.
> emails are on server because it is the server. but as i recall, they > are downloaded to client and deleted from server if so configured. I don't know of any client that does that. You may be thinking of POP, which is entirely different. The whole point of IMAP is to keep the master copy on the server where it's accessible from anywhere, and use local copies only as a cache.
Unfortutunately, as I mentioned, IMAP makes it pretty much impossible to implement this reliably, and efficiently. IDLE lets the client synchronize itself with the server only while it is connected to it. But, IDLE has nothing that lets the client synchronize itself with the server after it goes offline, then get reconnected later.
After connecting and opening a folder, an IMAP client has no efficient means of synchronizing its cache of the folder's content with what's on the server right now. The IMAP client has no means of determining a precise list of changes to the mailbox on the server since the IMAP client was logged on last time. There are several kinds of changes that the IMAP client /can/ quickly square away, but the protocol does not support actual syncing. It's not possible. IMAP is not designed for it.
I could get into the history of IMAP, how it came out, and the political reasons for that, but having my two remaining wisdom teeth pulled out would probably be a more pleasant experience.
> years ago, when i was using imap, i filtered on my client, not on > server. That's because standardized server-side filtering never really got going and isn't well-supported by any widely-used client.
And, it's highly unlikely that it ever will.
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