How to Fix “The Server You Are Connected to Is Using a Security Certificate That Cannot Be Verified” in Outlook

The error message “The server you are connected to is using a security certificate that cannot be verified” in Microsoft Outlook usually appears when Outlook cannot validate the SSL/TLS certificate used by the mail server. This can happen when setting up a new email account, after a server change, or following a Windows or Office update.

In most cases, this issue is related to certificate mismatches, incorrect server names, outdated root certificates, or misconfigured email account settings. Although the message may look alarming, it does not always indicate a serious security threat, especially if the email account previously worked without issues.

Fixing this Outlook certificate verification error in Windows 11 involves checking account configuration, validating certificate details, and ensuring Windows and Outlook trust the certificate authority. The steps below explain how to resolve the issue safely and restore normal email access.

How to Fix “The Server You Are Connected to Is Using a Security Certificate That Cannot Be Verified” in Outlook

The methods in this section focus on correcting certificate mismatches, fixing Outlook account settings, and restoring trusted certificates. Apply the steps in order and test Outlook after each method.

1. Verify the Certificate Details Shown in Outlook

The error dialog provides important clues.

1. When the error appears, click View Certificate.
2. Check the Issued to name.
3. Compare it with the incoming or outgoing mail server name in Outlook settings.
4. If the names do not match, Outlook will not trust the certificate.

A mismatch is the most common cause of this error.

2. Check Incoming and Outgoing Server Names in Outlook

Incorrect server names cause certificate validation failures.

1. Open Outlook.
2. Go to File.
3. Select Account Settings > Account Settings.
4. Choose the affected email account and click Change.
5. Verify Incoming mail server and Outgoing mail server names.
6. Ensure they match the certificate name exactly.
7. Save changes and restart Outlook.

Use the server names provided by your email provider.

3. Ensure SSL/TLS Encryption Settings Are Correct

Incorrect encryption settings can trigger certificate errors.

1. In Account Settings, click More Settings.
2. Open the Advanced tab.
3. Confirm the correct encryption type is selected for:
   • Incoming server
   • Outgoing server
4. Use SSL or TLS as recommended by your email provider.
5. Click OK and restart Outlook.

Incorrect encryption types can prevent certificate verification.

4. Update Windows 11 Root Certificates

Outdated root certificates can cause trust issues.

1. Open Settings.
2. Go to Windows Update.
3. Install all available updates.
4. Restart the computer.

Windows updates often refresh trusted certificate authorities.

5. Update Microsoft Outlook and Office

Older Office builds may not trust newer certificates.

1. Open Outlook.
2. Go to File > Account.
3. Click Update Options.
4. Select Update Now.
5. Restart Outlook after updates.

Keeping Outlook updated improves certificate compatibility.

6. Check System Date and Time Settings

Incorrect system time breaks certificate validation.

1. Open Settings.
2. Go to Time & language.
3. Select Date & time.
4. Enable Set time automatically.
5. Enable Set time zone automatically.
6. Restart the computer.

Certificates rely on accurate date and time.

7. Remove and Re-add the Email Account

Recreating the account refreshes certificate trust.

1. Open Outlook.
2. Go to File > Account Settings.
3. Select the affected email account.
4. Click Remove.
5. Restart Outlook.
6. Add the email account again using correct server settings.

This clears corrupted account configuration.

8. Temporarily Disable Antivirus Email Scanning

Some antivirus programs intercept SSL traffic.

1. Open your antivirus software.
2. Disable email scanning or SSL scanning temporarily.
3. Restart Outlook and test the connection.
4. Re-enable antivirus protection afterward.

If this fixes the issue, adjust antivirus exclusions for Outlook.

9. Accept the Certificate Only If You Trust the Server

This should be used with caution.

1. When the warning appears, review certificate details carefully.
2. Confirm the certificate belongs to your legitimate email provider.
3. Click Yes to accept the certificate if you trust it.

Avoid accepting certificates from unknown or suspicious servers.

10. Contact Your Email Provider or Administrator

Server-side issues may be the cause.

1. Confirm whether the mail server recently changed certificates.
2. Ask for updated server names or configuration details.
3. Apply any recommended settings.

Administrators can confirm whether the certificate is valid.

Final Thoughts

The Outlook error “The server you are connected to is using a security certificate that cannot be verified” is most often caused by incorrect server settings or certificate name mismatches rather than a serious security breach. By verifying server names, updating Windows and Outlook, and ensuring correct encryption settings, the issue can usually be resolved quickly.