Oab files not updating
This is called the Offline Address Book and is being generated on the Exchange server.
Due to various synching schedules, it can take up to 48 hours before you could actually see a change in Outlook after a modification has been made on the Exchange server or in Active Directory.
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.
Even though Outlook is the last in the chain, it is often the first level where the troubleshooting takes place as usually this is where the request is coming from.
In this guide, the relevant timings are explained and instructions are given in how you can directly force an update and resync, which can be very handy when troubleshooting or when you work in an Exchange environment which sees a lot of user mailbox mutations.
This means that in the worst possible scenario, an update to the Address Book won’t become available to the user until 48 hours after the change.
And since this website’s main focus is on Outlook, it makes sense to start with Outlook as well ;-).
Outlook is helping you complete other activities and does not allow the address book update to interfere.Synchronizing your Outlook (cached) address book with the Global Address book may fix these discrepancies.Instances of mail that is bounced back to the sender may also be fixed.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.