Cannot Start Outlook in Offline Mode - Resolved

When you switch Outlook to offline mode, you can read and compose email messages, edit your calendar and contacts, etc. This mode is particularly useful when you are traveling or when you have limited internet connectivity.

Opening Outlook without an internet connection 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 Start Outlook in Offline Mode’

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 to Open Outlook Offline

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 to Start Outlook Offline

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.

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About the Author: Tony Landry

Tony Landry is a Web Content Editor at Remo Software. He loves to write, edit, and manage content for users trying to troubleshoot and fix problems on Windows, Outlook, storage drives, and Cloud storage networks. With an aptitude that transcends writing, Tony is recognized as a Microsoft Outlook, Word, and PowerPoint expert. His comprehensive solutions…