Estonia provides everyone a smartcard with a per-person certificates on it, those could absolutely be used to exchange encrypted e-mails in general, but the rea

Estonia provides everyone a smartcard with a per-person certificates on it, those could absolutely be used to exchange encrypted e-mails in general, but the reason they aren't is because e-mail clients do not support it, there isn't a single e-mail client that comes even remotely close to that functionality. People resort to encrypted containers ASICE and attach those.