Outlook 2016: “Use Cached Exchange Mode” Option is Grayed Out?

To enable cached Exchange in Outlook 2016, follow these steps:
Open Outlook 2016.
Click the File tab.
Click Options.
Under the General section, click the Advanced button.
In the Cached Exchange Settings dialog box, select the Enable check box and click OK.

To enable cached Exchange mode in Outlook, open the Outlook Options dialog box and select the Cached Exchange check box.

To turn on Exchange cached mode, open the Exchange Management Shell and type:
Set-Mailbox -Identity -CachedModeEnabled $true

Outlook options may be greyed out if you have not installed the latest updates. To install the updates, click the gear icon in the top right corner of the Outlook window and select “Update Options.

Cached Exchange mode is greyed out because it can cause problems with your email and calendar settings. We recommend that you disable cached Exchange mode to avoid any potential problems.

If you don’t use cached Exchange Mode, your Exchange server will start to generate more and more log files. This can lead to a situation where the Exchange server will become unresponsive or stop responding altogether.

Cached Exchange mode settings are a set of preferences that determine how Outlook 2013 and 2016 cache email messages. They can be found in the Options dialog box in the Mail tab. The options are:
-Enabled: This option is selected by default and indicates that Outlook will cache email messages.
-Default Storage Location: This option specifies where Outlook should store cached email messages.

In most browsers, when you save a page, the Save button becomes greyed out. This is to remind you that you have already saved the page.

There is no definitive answer to this question since it largely depends on your specific situation and needs. However, in general, cached exchange mode can be useful if you need to reduce the load on your Exchange server or if you have limited bandwidth.

To disable cached mode in Group Policy in Outlook, open the Group Policy Management Console (GPMC) and navigate to the Local Computer Policy node. In the left pane, double-click on the Policies folder, and then click on the Outlook Settings policy. In the right pane, under the Conditions tab, clear the check box next to Enable Cached Mode.

Outlook can be automatically put into offline mode when it’s not connected to the internet. To get Outlook back online, follow these steps:
Open Outlook.
Click the File tab and select Options.
Click the General tab and under “Offline mode,” select the check box next to “When I’m not connected to the Internet.”
Click OK.

Outlook cached mode is a faster way to view your email, with some limitations. In cached mode, Outlook saves your email messages for a specific time period so that you can quickly access them the next time you open Outlook. However, if you delete or modify an email in cached mode, the changes won’t be saved and will need to be made again the next time you open Outlook.
Online mode is a more complete way to view your email.

To disable the .ost file in Outlook 2016:
Open Outlook 2016.
In the Navigation pane, click File.
In the File Types list, select the email folder you want to work with.
On the Home tab, in the Options group, click Advanced.
Under OST File Handling, clear the check box next to Use OST Files For Email Messages.
Click OK.

Yes, cached Exchange Mode can speed up Outlook. When Outlook is in cached Exchange Mode, it downloads the latest changes to the mailboxes and settings from the Exchange server rather than polling the server for changes. Polling can be slow depending on how busy the Exchange server is.

To determine if Outlook is cached in Exchange mode, you can use the Get-Mailbox cmdlet. This cmdlet will return information about the mailbox that you specify. If the mailbox is cached in Exchange mode, the Get-Mailbox cmdlet will return a value of Cached.