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

Outlook 2016 New Sync Slider Options

With Outlook 2013 we saw the introduction of the Sync Slider, which helps limit the size of OST’s by controlling how much recent mail was synchronized locally on the device. For Exchange accounts, this was 12 months by default, with the option to go down to 1 month or up to all mail.

In Outlook 2016, Microsoft added more sync options that allow for better storage management by only retaining this much mail on the device:

• 3 days;

• 1 or 2 weeks;

• 1, 3, 6, 12 or 24 months;

• All.

 

As before, this setting can also be adjusted using Group Policy.

Restricting Outlook Clients to Cached Mode

Some organizations prefer all Outlook clients to connect to their Exchange servers using Cached Exchange Mode (also known as offline mode) because clients in Online Mode can generate significantly more disk I/O traffic. Besides using Group Policy to control this from the client side, in Exchange 2007, 2010, 2013 and 2016 we can force all clients to use Cached Mode at the server end by running the following cmdlet:

Get-Mailbox | Set-CASMailbox -MAPIBlockOutlookNonCachedMode $True

The Set-CASMailbox cmdlet is used to configure client access settings on a mailbox. For example, we can configure settings for ActiveSync, Outlook, Outlook on the web, POP3, and IMAP4. The MAPIBlockOutlookNonCachedMode parameters, which is available only in on-premises Exchange servers, controls access to the mailbox by using Outlook in online or offline mode. Valid values for this parameter are:

• True: only Outlook clients that are configured to use Cached mode are allowed to access the mailbox;
• False: the state of the Cached mode setting is not checked before Outlook clients are allowed to access the mailbox (both online and cached mode are allowed). This is the default value.

However, be careful with this setting! If there are Outlook clients currently configured in Online mode and you set this parameter to True, they will receive the following error message and will not be able to connect until they change their Outlook profile to Cached mode: