Are there any limitation to email domains?

In the process of testing my customer signup, I stumbled across a problem while registering a user from
After the successful signup the verification email was not sent at all. I checked the logs and there was no errors.
I don’t know if that particular provider blocks some emails (i use AWS as a custom email provider) but I was wondering, are there some “suspicious” email provider that are automatically being blocked by auth0?

This can be tricky to track down. If you are using AWS as a custom e-mail provider then check the amazon logs. You should be able to see the message being delivered to the remote ( provider.

You may see it being delivered, in which case the problem is on the end, or you may see a greylisting type error or hard failure, that’ll indicate your next steps.


In the AWS logs I didn’t find anything relevant and the rejected send metric it’s 0 for the past 2 days.
I guess it was a temporary outage of that particular email provider or something broke briefly down the line because now the verification email works correctly (after I tried to manual resend the email from the user management panel).

Thank you for the fast answer.