It depends on your email client. If your email client is Chrome, then the pinning won't help you at all. >Chrome does not perform pin validation when the certi

It depends on your email client. If your email client is Chrome, then the pinning won't help you at all. >Chrome does not perform pin validation when the certificate chain chains up to a private trust anchor. https://chromium.googlesource.com/chromium/src/+/refs/heads/main/docs/security/faq.md#how-does-key-pinning-interact-with-local-proxies-and-filters https://chromium.googlesource.com/chromium/src/+/refs/heads/...