"Error sending email: Authenticated user is not authorized to send mail"


We are experiencing the issue discussed here: Failed to send email with "Authenticated user is not authorized to send mail"

However, we are not using Twilio for email delivery in any way (we do have a Twilio service, but it is not connected to our Auth0 account, and is only for texting).

Are there any other potential causes to this issue that we can troubleshoot? For instance, if the user is currently logged in, and they click the verify my email link (or forgot password), would the authenticated nature of the user cause this issue, or is this strictly an SMTP forwarding/sending configuration issue?

Thanks in advance.