Unique email required without disclosing emails to existing users

Question

In the standard online registration form, users must have a unique email for the site.

if the letter is already in use, a new user cannot be created with this letter, but it opens op for its use to find out which emails are members of the site (at least check if a specific letter is used).

Making sure the bot cannot request a bulk request is pretty simple - but is there a way to completely avoid it?

The best I can think of is to give the user the opportunity to generate a process with an unknown error and send an email to the address in the background, explaining the password reset procedures.

Is there a better option?

Update:

I want you to not remove a new user from the registration process in 99.9% of cases when the letter is really unique. Therefore, terminating the registration process to wait for the user to click the link in the email is not an ideal solution, although it may be viable in some cases.

Answer 1

Let the registration continue as usual, but in the confirmation email you should say:

"You allready have an accout bla, click here to cancel this registration, or continue with new registration and delete your current account" 

Thus, spammers never know which is better, and it is very convenient.

Answer 2

You can print something on the web page about this:

An email is sent to confirm your email address. Check your mail and click on the included (public) link.

those. you should probably check users email anyway, st you can do it at this point in the dialog ...

Answer 3

Many sites send mail to a specified email address containing a randomly generated verification code, and only accept user registration as soon as the user confirms that they were able to read this mail and receive a confirmation code. Typically, the mail contains a URL that the user can simply click to confirm.

If you do this, all you have to do is send a confirmation email to inform the user that they have already registered and explain the reset password procedure.

No matter what the web development framework may have, there is a package that processes confirmation letters.

Please note that you need to think about when the user had an email address and used it to register on your site, then they disappeared without changing the address and stopped using the address, and the other user now has an address and wants to register. There is no simple answer.

ADDED . You add that you do not want to receive a confirmation email so that registration takes place immediately. This requirement is contrary to unique email addresses because you do not know that the email address provided by the user is legal until it is verified, and it makes no sense to use the uniqueness of the user-selected string, which is simply formatted as an email address (if you want a unique username, it does not need to be formatted as an email address).

If you want to keep instant registration, you will only need to treat email addresses as an untrusted text field until confirmation. This means that every action that requires your site to send mail must be bombed if the user has not verified his email address. The confirmation process remains almost the same, but now, if the address is a duplicate, the user should be given the opportunity to combine the two accounts (which is difficult), or said that he should close one of the two accounts or change the email address associated with one of two accounts.