Cannot Open Outlook When Offline - Resolved

🕔 3 minutes read

If you can't open Outlook items in offline mode, this article is here to help. Read on for simple solutions to fix the issue.

Outlook can be used even when you’re not connected to the internet using ‘Offline mode’. In the ‘Offline mode’, you can perform tasks such as reading and composing email messages, editing your calendar and contacts, etc. This mode is particularly useful when you are traveling or when you have limited internet connectivity.

Working ‘Offline’ in Outlook is possible with the help of files called ‘OST’. They store a copy of the information on the server on your local computer. This information is what allows Outlook to be used without an Internet connection. Once internet connectivity is established, the OST file synchronizes with data on the server mailbox.

Error – ‘Cannot open Outlook when Offline’

Although Offline mode is useful, some users complain about issues when using it. This article focuses on a common error about ‘Outlook not starting when Offline’ and potential solutions. The error reads:

‘Cannot start Microsoft Outlook. Cannot open the Outlook window. The set of folders cannot be opened. The operation cannot be performed because the connection to the server is offline.

Before we go into solutions for the error, an important point to consider is that this situation mostly occurs when you are offline and try to start Outlook. It is not seen when you already have Outlook open and switch to offline mode.

Solution 1: Uncheck Favorites in Mail Navigation

Usually, when your folders are on your favorites list (mainly IMAP folders), Outlook waits for the server to be connected and thus creates problems when Outlook is ‘Offline’. To resolve this, turn ‘OFF’ Favorites on your Email navigation.

To do so, go to the ‘View’ menu and uncheck ‘Favorites’ in the folder pane. This helps resolve your issue in some cases.

Solution 2: Re-create the OST file

Sometimes, if your OST file is damaged, Outlook may have issues working in Offline mode. To resolve the Outlook error, you can delete the old .ost file and re-create the file. To delete the old .ost file, follow the steps below.

  1. Close Outlook and open Run by pressing the Windows + R keys
  2. Then type ‘%LOCALAPPDATA%\Microsoft\Outlook\’ and hit Enter
  3. Select the ‘.ost’ file and hit Delete to delete the file

Once you have deleted the old.ost file, you can create a new OST file easily by following the steps below.

  1. Go to the File menu and click on Info
  2. Select Account Settings > Microsoft Exchange > Settings
  3. Click on More Settings and choose Advanced Tab > Offline folder file settings
  4. Choose a destination to save your OST file and choose Ok.
  5. If you receive an error ‘.ost file couldn’t be found. Would you like to re-create it? Click ‘Yes’ and proceed.

This will create a new OST file. Now restart ‘Outlook’ and check if the issue is resolved.

However, if you do not want to go through the hassle of deleting your old .ost file and re-creating a new one, you can use OST to PST converter. This will help you repair the OST file and convert it to PST. After conversion, all Outlook items such as emails, contacts, calendars, etc. will be saved to the new PST file.

The software is designed to work with all versions of Outlook. It can be used to repair .ost files that are damaged due to synchronization issues or due to hardware or software errors in only a few clicks.

Avoid corruption in .ost files

To avoid corruption in .ost files, make sure you terminate Outlook properly. Also, make sure you don’t try syncing files with the server when the internet connection is too slow. Make sure the .ost file is within the size limit to avoid any corruption or damage. Additionally, if you have been dealing with large-sized PST file issues. Click to learn how to fix a pst file that is too large.

Frequently Asked Questions

Can I open an offline account on Outlook?

Yes, you can open an Outlook account without an email, to create one:
- Close Outlook and click Windows + R
- Type Outlook.exe /PIM<your profile name> and then click OK.

Does Office 365 work offline?

Yes, you can use Office 365 offline with Office 365 Business Premium or Office 365 Business subscriptions.

What is the switch between online and offline modes in Outlook?

To switch between online and offline modes in Outlook:
- Press Alt + F to open the File tab.
- Navigate to Work offline mode in the navigation pane.
- Press Enter to toggle between online and offline mode.

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John Harris

With a decade of experience in data recovery, John Harris, Senior Editor at Remo Software, is your go-to specialist. His focus includes partition management, Windows solutions, and data troubleshooting, delivering insightful content that serves both users and search engines.

John's expertise shines through in illuminating blog posts, untangling data loss intricacies across diverse storage platforms. His mastery extends from file systems to SD cards, USBs, and external drives on Mac and Windows.

Recognized by cpomagazine, everythingusb, and more, John Harris is your trusted data recovery guide. You can also find his articles featured on, computertechreviews.

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