Is a validation code always issued by the web GUI, is it also possible to use the ‘Authy’ app from Twilio? Or is the Twilio service only used to send an SMS?
Best answer by Erik Brink
Your question is briefly explained in the IAM administrator manual
There is an option to let the user fall back on email, for example if the mobile device is not available. In that case you should also configure email (SMTP) with the GUI.