I (and a lot of other people around here) are enthusiastic FastMail customers. Hit any of us up off-site if you are interested in a referral code (10% off). It costs money, but you get a really solid webmail experience with real human customer support. The CEO is active here on HN and posts pretty solid things like this: https://blog.fastmail.com/2018/02/14/email-is-your-electroni... I have a strong belief that FastM…
One issue I have with FastMail is the reuse of email addresses. It is possible to "hack" accounts on websites which were registered to expired email addresses by simply registering that email address anew and doing a password reset. This is very common in the domain space, where email addresses are publicly listed.
One is that you can send email as any other FastMail user, and it won't stop you. SPF passes and DKIM signatures signed (even for other customers' custom domains), totally impossible to tell the difference between a legitimate and spoofed message.
To be fair, DKIM is a borderline useless technology and doesn't really prove anything, but it still appears to be an intentional policy decision by FM to be "lax".
Interestingly enough they do track the real sender in mail headers (which I suspect enables them to mark their own official emails with "verified" badges), but it's a dynamic obfuscated value iirc so it's absolutely worthless for regular users.
It kind of makes my stomach churn when I consider that it's trivial for any other FastMail user to impersonate me, but OTOH, it's best not to be under the delusion that email is authenticated, so I'm staying with them.
Great service, despite my comments.