STMP, isn't. It has a lot of auxillery stuff and it's a nightmare to run a mail exchange. That being said, the excessive flexibility of the protocol stack can be a good thing if you know how to use it.
Given you use a postfix + opendkim setup I have devised a super neato near turnkey way to exchange email between mail exchanegs over lokinet while still coexisting with non lokinet mail exchanges.
To do all this install lokinet, persist the snapp keys in
/var/lib/lokinet/lokinet.ini in the
keyfile=/var/lib/lokinet/hs.private, then restart lokinet to apply settings. To get your
.loki address do a
dig @127.3.2.1 -t cname localhost.loki (after restart of course)
The changes needed for the mail exchange side is actually really simple. My dns configs (bind9 style) for my mail exchange are now effectively this: