Hello! I'm one of the founders. We do end-to-end encrypt email subjects. Sender/receiver addresses are not to ensure email goes to the right person. 10 GB drive is used across all Skiff products.
I've been using my personal domain on Skiff and been loving it personally! Simple to setup (nothing different to the usual) and it all works seamlessly!
Just that, it's one inbox in the Free tier. Since I'm using on my own domain, I prefer having one inbox for all addresses!
I use FastMail but would consider moving. Can I have unlimited aliases when using my own domain? I use their MaskedEmail function to generate aliases for each service and have > 150 at this point.