I actually ran mailbox and fastmail side by side before settling on mailbox. I think the UI is next to flawless. AFAIK they don't work on the UI themselves, the

I actually ran mailbox and fastmail side by side before settling on mailbox. I think the UI is next to flawless. AFAIK they don't work on the UI themselves, they use https://www.open-xchange.com/ https://www.open-xchange.com/