At this point you could|should run a proper mailsever with fetchmail. I'm running [0] specifically as a local archive solution. Now that can be accessed by Thunderbird.
docker.io/mailserver/docker-mailserver
Your link seems to be broken, though - is this the right one? https://hub.docker.com/r/mailserver/docker-mailserver
But yeh, this one.
One of the things I found so confusing about docker at first was how much information you could leave out of your image reference and docker would assume the rest. I'd prefer if it only assumed localhost, and never automatically assumed any remote registry. There's really no reason for docker.io to be special.
A simple redirect from https://docker.io/mailserver/docker-mailserver to https://hub.docker.com/r/mailserver/docker-mailserver would make so much sense.