How to Fix Invalid Certificate Warnings for Microsoft Office Servers
Question details
Users are receiving invalid security certificate warnings indicating that the certificate name does not match the Microsoft service hostname.
- Product
- Microsoft Office (Outlook, OneNote)
- Device & OS
- not provided
- Scenario
- Using Microsoft Office applications while an antivirus program actively inspects encrypted network connections.
- Observed behavior
- The antivirus software generates a warning stating that the security certificate is invalid or does not match the changing Microsoft service hostname.
Before modifying your antivirus network settings, confirm that your Microsoft Office applications and your antivirus software are fully updated to their latest versions.
Exclude Office Domains from Antivirus Encrypted Connection Scanning
Add the affected Microsoft service domains to the trusted addresses list in your antivirus software to prevent unnecessary certificate interception.
Antivirus software often inspects encrypted traffic by substituting its own certificate. If the Microsoft service hostname changes dynamically, the antivirus may flag it as a mismatch. Excluding the domain stops the antivirus from intercepting this specific secure connection.
Launch your antivirus software (e.g., Kaspersky Internet Security) and navigate to the main Settings menu.
Go to 'Network Settings' and locate the section labeled 'Encrypted Connections Scanning'.
Click on 'Trusted addresses' or the equivalent SSL-check exclusions option.
Enter the specific Microsoft domain causing the warning into the exclusions list and save your changes.
Close and reopen Outlook or OneNote to verify that the certificate warning no longer appears.
Verify Certificate Validity with Official Support
If exclusions do not work or you suspect a genuine security threat, verify the certificate details with Microsoft or your antivirus vendor.
Switch to WPS Office for a Hassle-Free Experience
If you are tired of dealing with complex server connections, background sync issues, and certificate errors in Microsoft Office, try WPS Office. It provides a lightweight, highly compatible, and user-friendly alternative for all your document needs without the heavy background service dependencies.
- 1. Visit the Official Website: Go to the official WPS Office website on your computer.
- 2. Download the Installer: Click the 'Free Download' button to get the lightweight installation package.
- 3. Install WPS Office: Run the downloaded installer and follow the simple on-screen instructions.
- 4. Open Your Files: Launch WPS Office and instantly open your existing Microsoft Office documents without format loss.
Frequently Asked Questions
Why does my antivirus flag Microsoft Office certificates as invalid?
Antivirus software often inspects encrypted network connections for security threats. When it intercepts traffic between Outlook and Microsoft servers, it substitutes its own certificate. If the Microsoft hostname changes dynamically or doesn't match perfectly, the antivirus generates a mismatch warning.
Is my computer at risk when I see this Outlook certificate warning?
In most cases involving legitimate Office applications and known antivirus software like Kaspersky, this is a false positive caused by SSL interception. However, you should always verify the certificate details to ensure it is not a genuine man-in-the-middle attack on your network.
Can I use wildcards to exclude all Microsoft domains in my antivirus?
It depends on the antivirus software. Programs like Kaspersky may not allow wildcard entries (such as *.microsoft.com) in their trusted addresses list. In such cases, you must add the specific individual hostnames that are triggering the warnings.
