Certificate information error

When I open Outlook in Win 10, I get this popup box “Internet Security Warning”
“The server you are connected to is using a security certificate that cannot be verified”
The target principal name is incorrect
view certificate
Do you want to continue using this server
I click ‘YES’
If I click 'view certificate , I get the following:-
" Certificate Information"
It says:- All the intended purposes of this certificate could not be verified
Issued to :- autoconfig.cp163173.hpdns.net
Issued by :- avast Web/Mail Shield Root
Valid from :- 15/06/2025 to 13/09/2025

And I click OK. My emails load even if I don’t click ‘ok’.

I followed Avast advice. Saved the Mailshield.der file. Uninstalled Avast free, Restarted windows. Reinstalled avast free. installed the Mailshield.der and still get the error.