Unable to Download Offline Address Book

The other day I was troubleshooting an issue where users were not able to download the Offline Address Book (OAB). After some troubleshooting steps, I ran the Outlook AutoConfiguration Test and noticed that the URL for the OAB was not listed:

Looking at the properties of the OAB, I noticed that Global Web Distribution was disabled and Virtual Directories was empty:

So what do these two properties do exactly?

• GlobalWebDistributionEnabled specifies whether distribution occurs to all virtual directories in the organization. If the value of the GlobalWebDistributionEnabled parameter is $True, distribution occurs to all virtual directories in the organization, and we cannot add values to the VirtualDirectories parameter;
• VirtualDirectories specifies the array of OABVirtualDirectory objects. If this parameter is specified, Version4 of the OAB must be generated.

Because, for some strange reason, none of these properties was set, there was no virtual directory for users to download the OAB from.

Remember that in Exchange 2013:

• OAB files are not stored locally on the CAS;
• OAB files are generated and stored in the Organization Mailbox first and later copied to the %ExchangeInstallPath%\ClientAccess\OAB\ folder on the Mailbox server responsible for generating the OAB;
• CAS 2013 proxies all OAB download requests to the appropriate Mailbox server (the one above);
• Outlook receives OAB URL from Autodiscover and reaches designated CAS 2013 through OAB URL.

So, without OAB URL users simply do not know where to go to get the OAB! Depending on the environment, we now have two options. The first is to specify which virtual directory(ies) to use:

Or simply enable Global Web Distribution:

After resetting IIS (or recycling the OAB application pool), if we run the Outlook AutoConfiguration Test again we should see the OAB URL:

To further test the OAB, beside manually downloading it in Outlook, you can write down the OAB URL, paste it into the address box in Windows Internet Explorer, add /OAB.xml to the end of the path, and then press Enter. The following is an example of what the URL and response resembles:

 

https://mail.domain.com/OAB/6b7ccc1d-7313-453b-9870-5e4708068e95/OAB.xml

How to Generate Exchange OAB Multiple Times a Day

The generation of the Offline Address Book (OAB) back in Exchange 2010 was based on a schedule set on the OAB’s properties. In Exchange 2013 (at least in CU9 at the time of writing this) and in Exchange 2016 "beta" we still see this property but it is no longer used:

 

 

Instead, Exchange Server 2013 OAB Generation takes place according to OABGeneratorWorkCycle and OABGeneratorWorkCycleCheckpoint properties configured at the Mailbox Server. According to TechNet:

• The OABGeneratorWorkCycle parameter specifies the time span in which the OAB generation on the Mailbox server will be processed. The default value is 8 hours;
• The OABGeneratorWorkCycleCheckpoint parameter specifies the time span at which to run OAB generation on the Mailbox server. The default value is 1 hour.

 

 

Maybe it is because English is not my first language, but it took me a while to understand exactly what the above means... Eventually I got to the conclusion that what the above text is trying to tell us is that, by default, Exchange updates the OAB every 8 hours. If I look at my environment, I can see this is indeed the case:

 

 

For organizations where recipients change at a considerable rate, this might not be ideal. Let us say that we want to want to update the OAB every 2 hours instead. To achieve this, we simply run the following cmdlet:

Set-MailboxServer “server” -OABGeneratorWorkCycle 00.02:00:00 -OABGeneratorWorkCycleCheckpoint 00:30:00

 

 

 

After a few hours, we can check the Application log and look for Event ID 17002 to ensure the OAB is actually being generated every two hours (Event ID 17001 shows when the generation started while 17002 when it completed):

 

 

 

Don’t forget that to set these properties across all your Mailbox servers that might be generating the OAB. The server hosting the arbitration mailbox with Persisted Capability “OrganizationCapabilityOABGen” is the one responsible for the OAB generation. For a non-DAG environment, you can use the following cmdlet to identify the OAB Generation server:

Get-Mailbox -Arbitration | Where {$_.PersistedCapabilities -match "oab"} | FT Name, ServerName

For a DAG environment, use the following one instead:

Get-Mailbox -Arbitration | Where {$_.PersistedCapabilities -match "oab"} | FT Name, Database

And then check which server currently has that database mounted:

Get-MailboxDatabaseCopyStatus “database”

Exchange 2010 EventID 9320 and 9359

During the generation of your Offline Address Book [OAB] you might see the following warning logged in the Exchange server responsible for generating the OAB:

Log Name:      Application

Source:        MSExchangeSA

Date:          05/07/2012 05:02:35

Event ID:      9320

Task Category: (13)

Level:         Warning

Keywords:      Classic

User:          N/A

Computer:      SERVER.domain.com

Description:

OABGen could not generate full details for some entries in the offline address list for address list '\Global Address List'.  To see which entries are affected, set event logging for the offline address list generator to at least medium.

And a similar warning to the one below for many of your users:

Log Name:      Application

Source:        MSExchangeSA

Date:          05/07/2012 05:02:08

Event ID:      9359

Task Category: (13)

Level:         Information

Keywords:      Classic

User:          N/A

Computer:      SERVER.domain.com

Description:

OALGen truncated or dropped properties for entry 'USERNAME' in address list '\Global Address List' because they exceeded the configured size limits for the version 4 offline address list.  The affected MAPI ids are:  8008. 

- \Default Offline Address List 

The possible affected MAPI IDs are:

• 0x8CD8000D = PR_EMS_AB_AUTH_ORIG

• 0x8008101F = PR_EMS_AB_IS_MEMBER_OF_DL_W

The example above with the 8008 ID is generated for each user in the OAB that is a member of a Distribution List [DL] and for each DL that has members.

This happened because the Active Directory attributes member and memberOf are not part of the truncated property list for regular groups. So when the OAB is being generated, this property is read but because Exchange can’t see it in the list, a 9359 event gets logged.

It looks like this is by design so, at the moment, there is no workaround or a way to suppress these warnings. The good news are that these warnings are expected, can be ignored and Microsoft has plans to address this!