Summary: Microsoft Outlook provides two different connectivity modes, Cached Exchange Mode and Online Mode, when you add or sign in to Outlook client on Windows or Mac using an Exchange Server Account. The Cached Exchange Mode, also referred to as Offline Mode or Work Offline, is the default connectivity mode for Exchange and Office 365 accounts. However, users can switch between Cached Exchange Mode and Online Mode by turning off the Cached Exchange Mode via Outlook options to resolve Outlook issues. In this blog, we have discussed the cached Exchange Mode with reasons and steps to turn off work offline mode in Outlook.
Cached Exchange Mode is an Outlook feature that works with Office 365 and Microsoft Exchange Server mailbox. It enables Outlook users to access and use their accounts when the internet is unreliable, slow, or unavailable. The mail items, such as emails, contacts, attachments, notes, calendar items, etc., are cached and stored locally in an Outlook OST (Offline Storage Table) file.
The changes made offline are stored in the OST file and synced with the Exchange Server when the system goes online or connects to the Exchange Server. By default, 12 months of your mailbox data is stored in the local cache. However, you can change this setting and control how many mail items Outlook can keep offline.
Cached Exchange Mode is also the default and recommended mode when adding and setting up an Office 365 or Exchange Server account. However, you can enable or disable the Cached Exchange Mode based on your preference for Office 365 or Exchange and switch to Online Mode.
IMPORTANT NOTE: If you use Outlook for Mac, the default mode is set to Cached Exchange Mode and cannot be changed.
Reasons to Turn Off Cached Exchange Mode
There could be various reasons to turn off the Cached Exchange Mode. For instance, when the local cache or OST file grows larger, it consumes the local storage space and may lead to performance issues in Outlook.
Cached Exchange Mode also works with Shared Folders in Microsoft Outlook 2010 and later versions. This allows Outlook users to add another user’s mailbox or shared folder to your profile. As a result, all items that you have access to are downloaded in the local cache (OST) that can significantly increase the OST file size.
However, an OST file becomes vulnerable to damage due to integrity issues caused by large size (oversizing).
Fun Fact: Local cache stored in .ost files is 50-80% larger than the mailbox size on the Exchange Server.
In addition, Outlook takes more time to fetch the information and may fail to locate emails in search. There could also be delays in mailbox synchronization, or sync errors may occur that can prevent users from sending or receiving new emails and lead to send/receive errors in Outlook or cause conflicts in shared folder.
An email message sent by an Outlook user is not sent immediately to the addressee. It may remain in the ‘Outbox’ of your Outlook account for up to one minute until the next synchronization starts. Users need to manually click the Send All button under the Send/Receive tab to send the email immediately.
However, you can resolve the sync errors and other common Outlook issues, such as send/receive errors, by turning off the Cached Exchange Mode in Outlook.
Turn Off Cached Exchange Mode in Outlook
Below we have discussed steps to turn off Cached Exchange Mode in Outlook 2007, 2010, 2013, 2016, and 2019 versions.
NOTE: Cached Exchange Mode may not be available in your Outlook if the administrator has disabled this feature, Windows Terminal Services are installed on Windows Server, or if you are not using Exchange, Office365, or Outlook.com account in Outlook.
Steps to Turn Off Cached Exchange Mode in Outlook 2013, 2016 or 2019
To turn off work offline or Cached Exchange Mode in Outlook 2013 and later, follow these steps,
- Navigate to File > Account Settings > Account Settings.
- Select the Exchange or Microsoft 365 profile under the Email tab and click Change.
- Uncheck the Use Cached Exchange Mode under Offline Settings to turn off Cached Exchange Mode in Outlook 2013, 2016 or 2019.
- Exit and restart Outlook for changes to take effect.
Steps to Turn Off Cached Exchange Mode in Outlook 2010
- Click the File> Account Settings> Account Settings.
- Select the Exchange account under the ’Email’ tab and click Change.
- Clear the Use Cached Exchange Mode check box under the Microsoft Exchange server to turn off Cached Exchange Mode in Outlook 2010.
- Restart Microsoft Outlook for the changes to take effect.
Steps to Turn Off Cached Exchange Mode in Outlook 2007
- On the Tools menu, click Account Settings.
- Select the Exchange account under the Email tab and click Change.
- Uncheck the Use Cached Exchange Mode check box under Microsoft Exchange server to turn off Cached Exchange Mode in Outlook 2007.
- Restart Outlook 2007 for the changes to take effect.
TIP: You can repeat the same steps to turn on the Cached Exchange Mode or enable the Work Offline feature in Outlook.
However, if your Outlook is stuck in Work Offline Mode or you can’t turn off Cached Exchange Mode, it indicates a problem with your OST file. For example, there could be integrity issues due to the large size, or the OST file may have become inaccessible due to sync errors.
In such cases, you can use an OST to PST converter software, such as Stellar Converter for OST, to restore email items from inaccessible OST files. You can also export the OST directly to Live Exchange Server or Office 365.
Cached Exchange Mode provides a seamless offline and online experience by creating a local cache of the user’s mailbox and Online Address Book (OAB). Although the Cached Exchange Mode is faster than the Online Mode, users may want to turn off the Cached Exchange Mode due to slow performance or insufficient storage space as the local cache (.ost) is 50-80% larger than the mailbox size on the server. This can also lead to integrity and synchronization errors that can prevent you from accessing the mail items from the OST files. In such cases, you convert the inaccessible OST file to PST using Stellar Converter for OST.
When cached Exchange Mode is turned off, you cannot work offline as Outlook requires constant internet connection to work. If the connection is unavailable or slow, the Outlook may not work properly. Also, you can’t access your mail items when the system is offline.
Cached Exchange Mode is recommended when you setup a Office 365, Exchange Server, or Outlook.com account in your Outlook client. It provides you offline access to your mailbox items even when the system is offline, connection is slow or unavailable.
Yes, it’s perfectly fine to turn off Cached Exchange Mode especially when you are facing issues with the Outlook cache and problem with Outlook performance due to oversizing.