The certificate for imap.googlemail.com does not come from trusted source

Running Thunderbird 140.8.0esr 64bit Windows 11 Home, v25H2 932GB storage 32GB ram i7-13700k Recently, I've started getting the following message every time I launch Thunderbird: "The certificate for imap.googlemail.com does not come from a trusted source." Digging into details I get: "you are about to override how Thunderbird identifies this site" "Location: imap.googlemail.com:993" "This site attempts to identify itself with invalid information" "Unknown Identity. The certificate is not trusted because it hasn't been verified as issued by a trusted authority using a secure signature." Digging deeper into the certificate I find the issuer is Bitdefender who I use for antivirus and VPN. However, the VPN shows no effect when enabled or disabled. The validity period is 2 Feb 2026 to 27 Apr 2026 l can get email, but cant send it. Is Bitdefender at fault? I'm stumped. What should I do???