Outlook Cached mode, an outdated cached copy of the GAL (Global Address List) may be used during the Admin Batch Migration process and this may result in "User not found in GAL" errors.
The cached copy of the GAL used by Outlook, when in cached mode may not be updated regularly and may contain outdated information.
Turning off cached mode for the Outlook Administrative profile will ensure that any GAL queries will go straight to the GAL, and not to a cached version, which may be outdated.
