I'm no docker guru - so I'm more than a little out of my depth in this case.
But clearly ssh is installed, because that's what I'm running, and the sshd allows a connect and I get a return from ls. So, it's working fine outside the container.

And I only need to execute doveadm sync inside the container. [Because that's where docecot/doveadm is installed.]

So, it sure seems to me that I've got everything in place, at least in terms of ssh/sshd. I'm not even sure how I'd ssh directly to a sshd inside the container.

AT> You need both. sshd where you try to connect to, and ssh on where you try to connect from.

AT> Aki