How to Fix the “Outlook cannot Connect to Server” Error?

Outlook creates an OST or Offline Folder file when configured with an Exchange Server profile in default Cached Exchange Mode. This OST file contains all your mail items, such as emails, contacts, attachments, notes, etc. It is encrypted by default with a unique MAPIEntryID GUID key, which is stored in the registry of your local system and Exchange Server.

Although OST file allows users to work even when the system is offline, it needs to authenticate the user profile by matching the MAPIEntryID GUID key with the mailbox server to allow access to the OST file contents and Outlook profile. If this authentication fails, Outlook cannot connect to the Exchange Server mailbox and displays the following or similar error message.

Cannot start Microsoft Outlook. Cannot Open Outlook Window. The set of folders cannot be opened. The file C:\Users\….\abc@xyz.com.ost cannot be accessed. You must connect to Microsoft Exchange at least once before you can use your Outlook data file (.ost).

Why Outlook is Not Connecting to Server?

Outlook may fail to connect to the Exchange server due to various reasons, such as:

• Network connectivity issues
• Server downtime or maintenance
• OST synchronization errors
• Damaged OST file
• A deleted or disabled mailbox on the Exchange Server
• Outdated Outlook or Windows operating system
• Damaged Microsoft Office or Outlook program files
• Corrupt Outlook profile
• Incompatible or faulty add-ins

Methods to Resolve Outlook Cannot Connect to Server Error

You can resolve the Outlook not connecting to server issues in Windows by following the given methods.

Notes: Back up your OST file to a safer location before applying these methods.Back up your OST file to a safer location before applying these methods.

Method 1: Restart the System and Check the Internet Connection

A simple system restart can sometimes resolve issues with Windows and other applications. So, restart your system. You can also restart router to reset the network connection. Then, check the internet connection by opening a web browser window. You can also try to log in to the mailbox server to check if it’s online or offline. After this, start Outlook. If you still see the same error message and Outlook cannot connect to the server, follow the next method.

Method 2: Update Outlook

Check and update Outlook to remove any bugs or incompatibility issues that may be causing connectivity problems with the mailbox server. The steps to check and update Outlook are as follows:

• Open Outlook.
• Go to File > Office Account (or Account in some versions).

• Under Product Information, select Update Options and then click Update Now.

If the Update Now option is not available in your Outlook client, download and install the Windows OS updates.

Note: If it is not fixed also try to reinstall Windows OS.

Method 3: Disable Faulty Add-ins

Incompatible or faulty Outlook add-ins may prevent or disrupt Outlook connection with the Exchange Server. To check if the error is caused by a faulty add-in, follow these steps:

• Press the Windows + R keys, type Outlook /safe, and press the Enter key or click OK. This will open Outlook in safe mode.

• Click File > Options.

• Click ‘Add-Ins’ and then click the ‘Go‘ button beside Manage: COM Add-Ins.

• Uncheck all Add-Ins and then click OK.

• Restart Outlook in normal mode.

If the error is resolved, activate each add-in one-at-a-time and observe Outlook for the error. This will help you find the faulty add-in. When found, remove it permanently.

Method 4: Use SSL (Encrypted) Channel

It’s important to ensure that the data exchanged between your email client and the server is encrypted. This is particularly important when sending and receiving sensitive information. Your organization’s policies or administrator may not allow server connection if the connection between Outlook and the server is not secure or encrypted. It may prevent or cause authentication failure leading to connectivity errors. You need to contact your administrator to know if your account requires SSL or encrypted connection. If yes, check these settings:

1. On the Tools menu, select Accounts.
2. Choose your account and then click Advanced.
3. Then, choose the Server tab.
4. Choose the Use SSL to connect checkbox under Microsoft Exchange and Directory service.

Method 5: Use the SARA Tool

You can use the Microsoft Support and Recovery Assistant (MSARA) tool to troubleshoot and resolve the connectivity issue. It tries to resolve the issue causing the error automatically or suggests changes that you can make to resolve the server connectivity errors. The steps to use this tool are as follows:

• Download the SARA tool and launch it.
• From the options, choose Outlook.

• Select Outlook keeps saying “Trying to Connect” or “Disconnected”.

• Click Next and the select Yes.

Complete the suggested changes to resolve the Outlook disconnected from Exchange Server issue.

Method 6: Create a New Outlook Profile

Outlook may fail to connect to the Exchange Server if your profile gets damaged. In such a case, you can create a new Outlook profile to fix the error. The steps are as follows:

• Open the Control Panel and search ‘Mail.’ Then, click on the ‘Mail’ option.

• Click ‘Show Profiles’ and then click ‘Add‘.

• Enter the Profile Name and click ‘OK.’

• Configure your new profile with your email account and click Finish.

• This will create a new Outlook profile.

Now open Outlook, choose the new Outlook profile and configure it. Then, check if Outlook is connecting with the server. If not, head to the next method.

Method 7: Repair or Reinstall Microsoft Office

Damaged or corrupt Microsoft Outlook or Office program files can also lead to connectivity errors. You can resolve this by repairing or reinstalling the MS Office program. Steps to repair MS Office installation are:

1. Open Control Panel and click Uninstall a program.

• Select Microsoft Office program and then click ‘Change.’

• Select ‘Repair’ and then click ‘Continue’ to repair the MS Office.

Now, try opening MS Outlook. If this does not resolve the Outlook cannot connect to server issue, you can try reinstalling the MS Office.

Steps to uninstall MS Office from the system and install it from scratch:

• Download the Office uninstall support tool and launch it.

• Click ‘Install.’ After the installation, it will launch the ‘Microsoft Support and Recovery Assistant’ utility.

• Click ‘I agree.’

• Select the Office version you want to uninstall and click ‘Next.’

• Follow the wizard to uninstall MS Office and then restart your system.
• The tool will reopen automatically and finish the uninstall process.
• Then, select the MS Office version you want to install and follow the wizard.

You may also download the MS Office setup and install it manually. Then, open the MS Outlook, configure your email profile, and check if your Outlook is now connecting to the Exchange Server.

Method 8: Rebuild or Recreate the OST File

Issues with the Outlook data file (OST) can also lead to the Outlook not connecting to the server issue. In such a case, you can try recreating the Outlook data file (OST). For this, locate the OST file and move it to another location or rename it with .bak extension.

After this, open Outlook. If your profile and the mailbox on the server are still active, a new OST file will be created and mail items will be synchronized from the server.

Conclusion

The ‘Outlook cannot connect to server’ error may render your Outlook account useless and result in a data loss situation, if not resolved. The error prevents you from accessing the Outlook account and mailbox items as it fails to connect to the Exchange Server.

We’ve discussed various methods in this post to troubleshoot the Outlook cannot connect to the server error. However, if your profile is deleted or disabled from the server, these fixes won’t work. In such a case, your Outlook cannot connect to the server and you receive an error. Also, the OST file linked with your account becomes orphaned and inaccessible. However, with the help of an advanced OST to PST converter tool, such as Stellar Converter for OST, you can extract and restore all mail items to a PST file. You can then import this converted PST into your new or different Outlook or Exchange profile and restore your mail items. The software also provides options to import mail items from orphaned or inaccessible OST file directly into a live Exchange mailbox or Office 365 or Microsoft 365 account.

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About The Author

Ravi Singh

Ravi Singh is a Senior Writer at Stellar®. He is an expert Tech Explainer, IoT enthusiast, and a passionate nerd with over 7 years of experience in technical writing. He writes about Microsoft Exchange, Microsoft 365, Email Migration, Linux, Windows, Mac, DIY Tech, and Smart Home. Ravi spends most of his weekends working with IoT (DIY Smart Home) devices and playing Overwatch. He is also a solo traveler who loves hiking and exploring new trails.