OK, https://github.com/loomio/mailin-docker/blob/master/Dockerfile is the Dockerfile. mailin listens on port 25 and calls a webhook. Listening on port 25 won't work on Cloudron, so that solution is unviable. We have to write a standalone script that scans IMAP mailbox and calls the wekhook. mailin code that calls the webhook is at https://github.com/loomio/mailin/blob/master/lib/mailin.js .
Thank you, works perfectly!! You guys are super heros. And thank to @vladimir-d for the fix on that particular issue! (though I couldn't see it in the release notes of the package)
One issue I had is that the instance was looking all broken after the package update, I had to delete website cookies and data for it to work (might have to do with all the CSS changes in the release).
