Comment by mmd45
bad summary. it prompted you to accept the certificate upon first use and then pinned it which is far different than what you are describing in terms of security implications.
bad summary. it prompted you to accept the certificate upon first use and then pinned it which is far different than what you are describing in terms of security implications.
TOFU for invalid/untrusted certificates is the equivalent of "go there anyway" in a browser Very different than explicitly trusting a Private CA. It means that skilled attackers can rely on unskilled users clicking the "trust me, it's fine" button. All so that someone skilled enough to set up their own email server and certificates doesn't have to configure their system securely?
This is about making bad things harder for unskilled users at the cost of raising the standard for service providers. If you can set up an email server, you can use easyrsa or step-ca or some manual openssl to create your own root CA. Or, register your self-signed email server as a trusted root CA.
Personally, I use easyrsa for my internal CA (with domain path constraints because I'm paranoid) and letsencrypt for my mail server, but I require VPN access to the user ports on the mail server.