Manual account activation because the "please click this link to confirm your email address" email somehow does not end up in my user's inbox, is one of the most frequent support requests I get.

I built an API (private for now) which offers a solution to these scenarios, and may work as an alternative to passive email validation.

Instead of receiving an email, users are asked to send an email to a unique email address to confirm their email address (this - by the way - also filters out temporary receive-only email addresses)

A proof of concept can be found here: https://confirm-email.progresso-ict.nl. I can imagine the API to be used for account creation, password recovery, signing up for newsletters, etc.

Even though, with a clickable mailto address, the amount of steps are equal or similar to receiving a confirmation email, my girlfriend tells me the method is cumbersome.

So, what does the HN community think? Other questions I still have to investigate are mainly security-related. Emails are spam-filtered by Amazon SES, yet have to test for spoofing.