Are you syncing with a PDA or smartphone? That is the typical cause...
otherwise, check your autoarchive settings - tools, options, other,
autoarchive and also on the folder properties. See
http://www.slipstick.com/tutorials/auto/archive.htm for screenshots.

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Diane Poremsky [MVP - Outlook]
Outlook Tips: http://www.outlook-tips.net/
Outlook & Exchange Solutions Center: http://www.slipstick.com/

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Do you sync your mailbox with a smartphone or pda?
http://forums.slipstick.com/showthread.php?t=39473

"Marbeck" wrote in message
...
I noticed that the appointments in my calendar are disappearing from my
calendar after 6 mos. How can I stop this from happening?