Using an alphanumeric sender ID for MFA SMS

Email, Voice, SMS IntegrationsMulti-factor Authentication

Last Updated: Feb 20, 2026

Overview

If using an Alphanumeric Sender ID when sending MFA SMSes rather than a phone number some countries prefer alphanumeric sender IDs over phone numbers for these kinds of SMSes. Customer may want to be able to use different mechanisms based on the user's country.
More information about Alphanumeric Sender IDs is here.

Cause

Solution

With SMS MFA, customer can choose the "Use Messaging Service" option as the "SMS Source" in Auth0 dashboard. This will let them use Twilio Messaging Service which can dynamically change the source (between phone number and alphanumeric code, etc) depending on the country: https://www.twilio.com/docs/messaging/services/services-send-messages

If that doesn't work for the customer for some reason, the only other option would be to use a Phone Message Action.