Why does it take up to 2 days for new users to appear in Outlook?

Ever wondered why it can take a day or two before new users/groups/contacts/public folders show up in the address book in Outlook?

First of all, this affects Outlook clients running in cached mode as they use the Offline Address Book (OAB) for the Global Address List (GAL) rather than Active Directory which will be used when Outlook is in online mode.

Secondly, believe it or not, this is by design and is due to the way the OAB is generated and distributed to clients.

The OAB update process is something like this:

The OAB generation server is (by default) set to update the OAB at 5am daily.  It updates the OAB to a local folder.

Each OAB distribution server (regardless if you have only one or many) polls the OAB generation server every 8 hours (default) for updates.

Outlook in cached mode will download OAB updates when started or every 24 hours if left open (it's a bit more complex than that but I don't want to get bogged down here).

An example:

John creates new distribution groups on a Tuesday morning.  On Wednesday morning at 5am the OAB generation server updates the OAB with the new distribution groups.  Let’s say we’re unlucky and the OAB distribution servers don’t update their files for nearly 8 hours so just before 1pm Wednesday.

John's boss leaves his workstation running all the time with Outlook open.  Outlook checked for updates to its OAB on the Wednesday morning but the distribution groups weren't in the updates available on the OAB distribution servers at that time.  John's boss starts moaning about how John hasn't created the distribution groups right or that Exchange sucks or something and it's not until Thursday morning that John's boss's Outlook OAB updates with the DGs.

You should be able to see now why it’s possible for up to 2 days to pass before addresses appear in Outlook.  Throw in multiple sites and you could potentially add a few more hours into the equation.

What can you do to speed this up?

1. Reduce the OAB virtual directory polling internal from 8 hours to maybe 2 hours.  Not recommended as it adds overhead to client access servers during working hours.

2. Change the OAB update schedule to custom and run it multiple times per day.  Not recommended in larger environments due to the extra processing it can add to the OAB generation server but in smaller environments shouldn't matter.

3. Change the OAB update schedule to custom and run late in the evening, say 9pm.  You should try and set the schedule outside of backup windows and maintenance intervals.  By setting OAB generation schedule to 9pm, at the latest the OAB distribution servers should pick up the updates by 5am the next day making them available to Outlook clients when they’re started.

This is true to Outlook 2010 and Exchange 2010 and should also be for their 2007 equivalents.  Outlook 2003 gets its OAB updates from public folders but really, are you STILL using Outlook 2003?

This post in its entirety is the copyright of Roland Paix. I don't mind if you link to it but if you copy any of the content you must provide a link to the post and credit me appropriately.