[Courier-imap] message is no longer available on server

[Amit]

Hi   I have courier-imap-3.0.8, squirrelmail-1.4.5 and qmail-ldap running fine on my server. However, since last few days, I am facing this problem. Sometimes, when a new message arrives in my Inbox, Outlook Express automatically shows it as marked for deletion by striking it through and when I click on the message to view it, I get the following message -   This Message is no longer available on the server ....   IMAP servers expire messages periodically ......or it may have been deleted from the server............etc   However, at the same time, If I log on to squirrelmail, I can see the message, its very much there and I can read it too!. But If I perform any operation with the message, lets say if I move the message from Inbox to another folder, the message gets unmarked and becomes readable from Outlook Express.   I feel this problem probably arises when the number of messages in the INBOX folder gets over a certain limit. Right now, my INBOX folder has 4470 messages.   I would like to know why this happens. Is this an OE problem ? I'd appreciate if anyone can suggest a way to deal with the issue.   Thx,   Amit