Hello Nigel,
Let's work together to fix it. Refer this article: https://support.avg.com/SupportArticleView?urlname=AVG-Troubleshoot-invalid-email-certificate and follow the steps suggested there to check if that helps.
AVG required a restart today 28 August for a new update. I ran restarted the computer and had the same problem as earlier:
I received a "internet security warning" when I opened Outlook with the message:
"The server you are connected to is using a security certificate that cannot be verified.
A certificate chain processed, but terminated in a root certificate which is not trusted by the trust provider."
I checked the Trusted Root Certification Authorities store and the SSL certificate "AVG Web/Mail Shield Root" was gone following the restart with only the one AVG certificate in the store "AVG Technologies".
As I did above, I exported the certificate and had to insert it again.
I recently encountered the same issue on Outlook 2023. After importing the certificate, Outlook still showed the same problem (as seen described above). The fix was to remove the account from Outlook and then add it back. This worked for all of my accounts.
I use Outlook 2010 on Windows 7 using POP3/SMTP with SSL.
I receive a "internet security warning" when I open Outlook
"The server you are connected to is using a security certificate that cannot be verified.
A certificate chain processed, but terminated in a root certificate which is not trusted by the trust provider."
There are two options: "View Certificate…" or "do you want to continue using this server?"
If I click continue using this server Outlook works. If I close Outlook and restart the same message appears again.
If I turn off email shield I receive emails fine. If I change my email settings removing SSL I can use the email shield.
This occurred after latest AVG application update.
If I view the certificate in the general tab it has "Windows does not have enough information to verify this certificate."
Issued to: * (it has my email address minus username i.e. *hotmail.com)
Issued by: AVG Web/Mail Shield Root
Valid from 5/02/2018 to 6/04/2021
There is an option to install certificate.
AVG required a restart today 28 August for a new update. I ran restarted the computer and had the same problem as earlier:
I received a "internet security warning" when I opened Outlook with the message:
"The server you are connected to is using a security certificate that cannot be verified.
A certificate chain processed, but terminated in a root certificate which is not trusted by the trust provider."
I checked the Trusted Root Certification Authorities store and the SSL certificate "AVG Web/Mail Shield Root" was gone following the restart with only the one AVG certificate in the store "AVG Technologies".
As I did above, I exported the certificate and had to insert it again.
Feel free to contact us if you need assistance with AVG.
Have a nice day!
Nigel, it is so unfortunate that the issue has recurred.
Please accept our apologies for the inconvenience caused.
Are you still facing the issue after inserting and exporting the file?
Keep us posted.
We're sorry to know that, Nigel. However, would you be so kind to ensure us that the issue with Outlook certificate error is fixed currently?
I initially tried that in Outlook 2010 and this enables you to import a "Digital ID" with file types of .pfx or .p12 file. "Import existing Digital ID from a file". Not a SSL certificate with a .der file type. As I said above I couldn't see a way to import into Outlook.
I recently encountered the same issue on Outlook 2023. After importing the certificate, Outlook still showed the same problem (as seen described above). The fix was to remove the account from Outlook and then add it back. This worked for all of my accounts.