"The security token included in the request is invalid" error when sending email from AWS SES Email provider

Problem Statement

We did not make any configuration changes on our AWE SES email provider, but the emails failed with the error “The security token included in the request is invalid”.

Cause

If the credentials haven’t been changed by you or another admin and there have been no configuration changes on your AWS SES end, you might need to check if you have a Password Manager enabled.

Password managers may have an option enabled to autofill passwords and it may mistakenly fill in and update the credentials inputs on the Auth0 Dashboard Email provider settings when accessing that page. You can search through the tenant logs, looking for Update the email provider errors.

Solution

Disable password manager autofill and autosubmit.