Hello,
I have two smtpd nodes, i'll call them A and B.
Node A is exposed to internet, Node B is not and is relaying everything
to node A.
The action line on node B looks like this :
action "send" relay host smtps://[some kind of ipv6] srs
On Node A, i have a match for that "some kind of ipv6" that does a relay
for everything that comes from node B.
match from src [some kind of ipv6] action "send"
action "send" relay srs
It always helps if you show the whole configuration.
Do you have a certificate for A-[some kind of ipv6]? Since it is a IP
and not a domain I assume it is self-signed? Does B know about your CA?