Re: Getting rid of the sequence numbers

[Cyrus Daboo]

Hi Timo,

--On Friday, February 21, 2003 7:34 AM +0200 Timo Sirainen <[EMAIL PROTECTED]> wrote:

| Actually in some situations relying on sequence numbers could even lose
| messages. Suppose a client (maybe a webmail) showing messages 1..10 on
| screen. Next-button would load the next 10. If the IMAP connection got
| closed before next-button was clicked and some of those messages were
| expunged before connection was up again, fetching 10..20 would have
| skipped over some of the unread messages.

Well this is of course a bogus situation because no client can cache sequence numbers across different connections - they have to use UIDs for that. Most of the webmail solutions I know of that do not maintain persistent IMAP connections do use UIDs.

This issue is in fact one of the major disadvantages to relying on sequence numbers given the propensity of network devices (e.g. firewalls, cable/dsl modems etc) to timeout idle connections at an interval less than the IMAP 30 minute timeout. Those devices pretty much force online clients to have to NOOP poll at a much shorter interval than they ought to to keep the connection alive. If the connection does die, the client is forced to effectively do a full resync of its cached state (or just throw it out and start over) if it attempts to recover the lost connection. This problem has been a major headache for me over the last few years.

--
Cyrus Daboo