Exchange gal not updating
This situation however is extremely rare since the default maintenance time on Exchange is at AM and updates and downloads are usually performed during working hours.
In this case your global address book will update each time Send/Receive is pressed.
When you have Cached Exchange Mode enabled, Outlook by will by default cache the main Global Address List as well.
Please visit the document on How to turn on or off Cached Exchange Mode for (Outlook 2007, Outlook 2010, and Outlook 2013).
Outlook 2011 does not use Exchange Cached mode and directly connects to the Global Address Book (GAL) via LDAP connection.
Please use the steps below to update your Global Address Book.In order for some GAL entries to show up properly you may need to turn off Cached Exchange Mode.