Arnt Gulbrandsen schrieb:
Antonio Cambule (St�ber Software) writes:
Sorry that I thought there could be an higher meaning behind that, supposed on quasi standard protocols like IMAP.
Of course there is a reason, and I'll bet it has been explained a few times on the mailing list. The archives are at http://www.washington.edu/imap/imap-list.html. Look at the years 1990 to 1994.
Be sure I did If I had found an answer I wouldn't have asked.
I don't want to criticise the protocol but understand why things should be done as they are described. Maybe there was an other way I don't know to keep the list updated and that is what I wanted.
As follows:
In a network protocol, it's better if all servers behave the same way than if some servers behave one way and some behave another.
Since some IMAP servers do not have exclusive control over their mail stores, some IMAP servers are not able to detect whether mailboxes appear or disappear. For example, any IMAP server that publishes USENET via IMAP does not, and restoring a backup frequently changes a mailstore directly.
It follows that IMAP must make a choice:
1. Let servers behave differently wrt. mailbox disappearance.
2. Require that all servers must check that a mailbox exist when referring to it. This would make the LIST command very very slow on quite a few servers.
3. Require that a disappearing mailbox does change the subscription list.
Which is better?
That's not the Problem and I think you know what I mean.
Why should a server give an answer of 20 subscribed mailboxes if only one of it may be existent?
It's not a question of disk space but of performance.
Oh. Make LIST perform well too, then.
Arnt
Ok. That's an answer.
Question on point 2:
I'm developing an Mailserver including the IMAP protocol (sure I want the server to be protocol conform). But how can I give back an good answer to an LIST command if I don't check the existence of that Mailbox or mailboxes. I suppose I send back all mailboxes requested in List command because of the performance and check the very existence of an mailbox on incoming Select command. Would that be better or is there an other way?
-- regards
Antonio Cambule Development Team
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