Verification email not always sent

We had several users sign up yesterday. In the overwhelming majority of users, the verification email was sent. I can see this by looking at each user record (history) and seeing the event “Success Verification Email” happening right after “Success Signup”.
However there were three users who never got the email, and the “Success Verification Email” event is not in their history.
The status switch for the Verification Email template is on.
Has anyone seen this? Where an occasional signup does not get the verification email?

That log event represents an action by the user so it will appear when the end-user completes the verification email. This means that the lack of this event in their history is by itself not an indicator that something is wrong as a user can technically decide to not verify their email.

In other words, you can’t use that log type to check if emails are sent, you can only use it to check which users completed the flow. There’s a log type (fv) for failed verification email that may be more relevant, but again may also not be present in your history if the issue was the that the email was sent with success (from the perspective of the service), but then not delivered to user inbox (for example, due to filters on the receiving end).

Having said all of that there’s a few things you can check:

  • ensure that you’re using your own email provider in the tenant settings (the default built-in one is not suitable for production).
  • check the logs of your own email provider in order to confirm that the logs show that the Auth0 service requested an email to be sent for that user.
  • see if there’s any pattern in the users that did not complete verification; do they all have an email address in the same domain? is it a corporate domain likely to include additional email filters?
  • enlist the collaboration of an impacted end-user and asked them to check their spam folder.