weirdness after reconstructing

[David Carter]

On Fri, 16 Apr 2004, Robin M. wrote:

> > In addition to this, I noticed that now everything is unread, which I can
> > deal with but if I mark it as read, close the email client and come back
> > its marked as unread again.
> >
> Hi I am curios can you explain your mails being flagged as new more.

The original report sounds like database corruption or a mismatch between
the configured seen database type and what was on disk.

> I am having the same problem, but only with squirrelmail and Outlook
> express, Outlook and thunderbird are fine. I only notice this happen
> when I compose a message or reply to a message.

I don't know about squirrelmail, but the problem with Outlook Express is
that it makes two concurrent IMAP connections to a given mailbox. One of
these IMAP sessions is used to generate lists of messages within a mailbox
while the other is used to fetch individual messages. I infer the idea is
to improve concurrency on slow dialup links (OEs intended audience), in
case the message IMAP stream gets blocked up downloading a big message.

The problem is that the IMAP session which fetches messages updates the
Cyrus seen database, but these changes aren't picked up immediately by the
other IMAP session. The Cyrus imapd only calls index_check() on certain
IMAP operations (it follows the IMAP specification to the letter!).

A patch is floating around which causes imapd to call index_check() more
frequently (specifically on all IMAP FETCH and STORE operations):

  http://asg.web.cmu.edu/archive/message.php?
     mailbox=archive.info-cyrus&msg=19703

I used this patch for a number of months and it certainly fixes the
problem with OE. It does involve a bit more work for the IMAP server, but
I can't say that I can see any measurable difference on our systems.

The only problem with this patch is that it causes unsolicited EXPUNGE
events to (non UID) FETCH and STORE operations, which isn't allowed.
This breaks legitimate concurrent access to mail folders. I have an
updated patch which fixes this problem if anyone is interested.

-- 
David Carter                             Email: David.Carter at ucs.cam.ac.uk
University Computing Service,            Phone: (01223) 334502
New Museums Site, Pembroke Street,       Fax:   (01223) 334679
Cambridge UK. CB2 3QH.
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