I used to pay for Fastmail.fm as a mail service. It wasn't that cheap, but the top account which gave plenty of space and the ability to have my own domain wasn

I used to pay for Fastmail.fm as a mail service. It wasn't that cheap, but the top account which gave plenty of space and the ability to have my own domain wasn't expensive. They kept the old versions of their web interface alive for many years after the active development of the 'default' moved on to different designs. Which was very helpful for me, as I much preferred their non-Javascript laden interface and kept the one I started with for many years of use. I only moved on when I tripped their anti-spam/account hacked filter and didn't have my business e-mail for three days because the messages the interface gave me were misleading. Apart from that, I was very happy with them and they were very sensible about what they'd do with the interface. As an aside, I think $12 a year is unrealistic for paid webmail as you'd need a good level of scale to make it pay for such a small amount. You're already talking about a service a small number of people want (interface staying the same and willing to pay for it) I'd expect you'd find the same people would be willing to pay enough to make the service worth running.