Why does it take a long time for Exchange 2010 and Outlook 2010 to sync with each other within our office?

When I create a new message in Outlook 2010, and "use cached exchanged mode" is UNCHECKED, all new users appear immediately when I click on the To: button.

When I create a new message in Outlook 2010, and "use cached exchanged mode" is CHECKED, it takes several hours before new users appear in the To: list.

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Glen KnightConnect With a Mentor Commented:
This is because you use the offline address book when in cached mode.

This is only updates once every 24 hours and downloaded once every 24 hours unless you manually rebuild and force a manual download.
Cached mode uses a cached version of the GAL called the Offline ADdress Book, exchange only updates the OAB once a day at 5AM by default, hence the outlook delay
MegaNuk3Connect With a Mentor Commented:
Outlook will only download the OAB once every 24 hours, normally when it is opened.

You also have to wait 8 hours for your CAS to copy the web version of the OAB from the generating server for your cached mode Outlook 2010 clients to use. So by 1PM you can restart Outlook or manually download the OAB (normally F9 in Outlook) and you should see the changes
As demazter says, you can force the update and get it ready for download by your Outlook clients usually within 15 minutes based on the amount of data in your GAL. 1min per 10000 objects is what I have been seeing, but you might see different based on how much detail your GAL objects have and how fast your hardware is.
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