Outlook Express and Seen database - And Outlook Express and Cyrus in general

[John Alton Tamplin]

Steve Hanson wrote:

> There was some discussion on the list in the past about problems with 
> Outlook Express not interoperating well with Cyrus due to it 
> corrupting the seen database by using multiple concurrent connections, 
> confusing the caching model in Cyrus.
>
> Our desktop support people are trying to stump up support for making 
> Outlook Express on Windows be the preferred email client - which at 
> the moment is more or less Eudora.
>
> Does anyone have opinions about whether Outlook Express 6 still causes 
> the seen database corruption with Cyrus 2.1.10 or later?
>
> Also if anyone has any other bad (or good) experiences with Outlook 
> Express as a client with Cyrus I'd like to hear about them.

I don't know of any discussion of database corruption, but the problem 
is that Outlook would be confused about the seen flags since it uses two 
different IMAP connections to process them and Cyrus keeps all that in 
memory per-process.  The only "corruption" issue I have seen is that 
twice we had a user being unable to delete messages from a folder that 
was perfectly fine (and other IMAP clients could delete messages without 
a problem), and after deleting the subscription and resubscribing the 
problem went away.  Research suggested this was a race condition in OE 
that had nothing to do with the IMAP server other than perhaps 
participation in the timing aspects of the race condition.  It was not 
reproducable and has not happened in over 2 months.  (This is with a 
user base of 2300 users, ~250 connected at any one time, and 90G spool 
space).

Most of our users use OE6, and there have been no issues I am aware of 
in the 3.5 months we have been running it since I applied my patch for 
flushing the in-memory seen flags state to disk whenever it changes and 
checking the seen flags on disk for updates before replying to the 
client.  This is with 2.1.11 and 2.1.12, and if you need the patch I 
would be happy to send it to you.  Note that this will increase I/O 
traffic so you may not want to apply the patch if you have little margin 
for I/O bandwidth.  Our server is so lightly loaded (it was sized to 
handle the load when we were running UW-IMAP) we didn't see any 
noticable difference, but I know the traffic will be higher.

-- 
John A. Tamplin                               Unix System Administrator
Emory University, School of Public Health     +1 404/727-9931