Ultimate Help Desk
PC performance issues? Home Network Setup needed? Get on-demand IT help 24/7 NEW! Easily regain email account access, restore lost data, and more!
Troubleshooting email client warnings about invalid server certificates
Applicable for: Windows
After installing your Norton product, some third-party email clients may show that the mail server certificate is invalid when you send and receive emails.
Email Protection in your Norton product uses an advanced scanning method for incoming and outgoing emails over SSL/TLS secured connections. Most third-party email clients have their own certificate stores and may require extra configuration to avoid warnings about invalid mail server certificates.
For Mozilla Thunderbird, follow the steps below to stop warnings about invalid mail server certificates by exporting the Email Protection certificate, then importing it into your email client's certificate store.
Mozilla Thunderbird
STEP 1: Export the Email Protection certificate
-
Press the Windows + E keys to open the open Windows Explorer.
-
Navigate to the following location:
C:/ProgramData/Norton/AntiVirus/
The ProgramData folder could appear hidden. To display hidden files and folders, refer the Microsoft Support article: Show hidden files. -
Find the following certificate file:
wscert.der
-
Copy and save the file on your Desktop.
-
Go to Step 2 to import the certificate file in your email client.
STEP 2: Import the Email Protection certificate to your email client
-
In Mozilla Thunderbird, click the menu icon (three lines) > Settings.
-
On the left pane, select Privacy & Security.
-
Scroll down to the Certificates section, and then click Manage Certificates.
-
On the Authorities tab, click Import.
-
Locate the wscert.der file that you saved, select the file, then click Open.
-
In the alert that appears, check Trust this CA to identify websites, and then click OK.
-
When the Certificate Manager screen appears again, click the Servers tab.
Ensure that there is no entry for Norton Email Protection.
-
If any entry exists, delete it and click OK to save the changes.
The Email Protection certificate from Norton is now imported to Mozilla Thunderbird.
If you are seeing certificate warnings or errors in Microsoft Outlook, we recommend you reinstall your Norton product:
Microsoft Outlook
For detailed instructions on how to reinstall your Norton product using the Norton Remove and Reinstall tool for Windows, follow the steps below:
Once your Norton product is reinstalled, open Microsoft Outlook and check if the issue persists.
Last modified: 07/03/2025
Was this article helpful?