– 9 out of 10 times cached mode is the way to go
– Ensure your OST files are not being cached or are part of a roaming profile, they can become corrupted and cause headaches
– Most OST issues can be solved by changing from cached mode, to non-cached mode, run Outlook for a while, then change back to cached mode. Worst case, delete the OST but this can be bad if the Exchange server is over a WAN link
– #1 issue for me, the Offline Address Book is only built at midnight and downloaded once per day by Outlook. You can schedule the OAL to update more often, but users will usually always see a lag between when new users are provisioned and they are seen in the GAL. There is a registry hack to make users always use the online GAL instead of the OAB, but this is NOT recommended for laptop users.
– Terminal Servers and of course Citrix servers do not use cached mode if Office was installed after TS was changed to application mode. If you see cached mode on a TS in app mode, do not use it.
If you make frequent changes to the Offline Address Book, you may want to modify the way that Outlook 2003 computers on your network access the Address Book. You can disable the downloading of the Offline Address Book and force the Outlook 2003 computers to use the online Global Address List when they use Cached Exchange Mode.
To do this, add the following registry value to the Outlook 2003 computers:
HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\11.0\Ou tlook\Cached Mode
By using the value 0 (zero), the Offline Address Book is not downloaded automatically, and Outlook must contact the online Global Address List. For additional information about the values for the DownloadOAB registry parameter, click the following article number to view the article in the Microsoft Knowledge Base:
KB823580. How to configure how the Offline Address Book is downloaded when you use Outlook 2003 in Cached Exchange Mode
As per this article, if Offline Address Book (.oab) files were previously downloaded and were associated with a MAPI profile for Outlook, this setting will not have the correct effect. To use this setting, you must set the registry value, remove any .oab files from the local computer, and then synchronize.