I ended up just doing skiff free version for the time being. It is allowing me to use custom domain and it gives me a couple skiff aliases I can use. Only thing I don’t like is it forces me to use the app and no notifications without Google play services.
Yeah. Not sure it will be a long term solution. But needed something for now while I migrate away from mailbox.org. Thankfully I didn’t use the mailbox.org aliases much so it is pretty simple to switch providers.