I would like to know how to send bulk email verification email to existing customers. Also If a new customer registers how do I send the email verification email? It is not automated at the point.
You can follow a technique!
Under User Verification => Tools tab, we have an option called Mark all existing users as verified. You can turn on this setting and lower the interval time.
You can check the status and track how many users are automatically verified under the Users section. Also, if you want, you can mark a user unverified again.
Don't forget to turn off the setting if you don't want a user to pass the verification process without verifying.