Thanks for the response. :) My guess is that more users will be alienated simply because it's, well, alien. They're not used to it. I've never heard of a servi

Thanks for the response. :) My guess is that more users will be alienated simply because it's, well, alien. They're not used to it. I've never heard of a service doing this. But if you think about it it's not that onerous. After a user submits their email address I have a page with <a href="mailto:proof@example.com?subject=SecretCode">Click Here To Prove You Own This Address</a> which hopefully will work on a good percentage of people's machines and smart phones. I don't know how many people have mail clients installed. If they don't have a mail client, I'll still have a nicely rendered example email so they know they just have to put the secret code in the subject line and click send. This is of course harder than clicking a link, but then again people are used to receiving secret codes and having to copy/paste them into the website. And again there are CAPTCHAs to consider when sending people emails, which are hard to solve and give up privacy and effectively lock you into Google. For some small services I've set up over the years I also have had a lot of people complaining about not receiving emails despite using very reputable services like Postmark and Sendgrid. It's hard to say percentages though. I agree I'll lose more users, but I think it's more a matter of people not being used to it then it being a technically inferior solution from a UX perspective. Anyway thanks again!