---
"@context": https://schema.org
"@type": TechArticle
"@id": https://www.twilio.com/docs/api/errors/21738#article
headline: "21738: Brand Registration Failure: 2FA Email Undeliverable"
url: https://www.twilio.com/docs/api/errors/21738
inLanguage: en
dateModified: 2026-04-20T06:45:15.000Z
author:
  "@type": Organization
  name: Twilio Developer Education Team
publisher:
  "@type": Organization
  name: Twilio
---

# 21738: Brand Registration Failure: 2FA Email Undeliverable

Log Type: APPLICATION

Log Level: ERROR

## Description

This error means the Authentication+ verification email for your A2P 10DLC brand contact could not be delivered. Your brand contact must receive and complete this 2FA step before brand registration can continue.

### Possible causes

* The `brand_contact_email` value is invalid or contains a typo.
* The mailbox is inactive or cannot receive external email.
* The recipient's email server rejected the verification message.

### Possible solutions

* Confirm that the brand contact email is correct, active, and able to receive external messages.
* If the email address is incorrect, update `brand_contact_email` in the associated `us_a2p_messaging_profile_information` bundle for the brand.
* If this is a new brand registration, trigger Authentication+ again after updating the email address by creating a new Brand 2FA verification request.
* If the brand contact still did not receive the email, resend the verification email from Console under Messaging > Regulatory Compliance > Brands.
* If you are re-verifying an existing brand, update `brand_contact_email`, move the associated bundle to `pending-review`, and call the brand update endpoint.

#### Additional resources

* [Troubleshooting A2P 10DLC Standard and Low Volume Standard brands](/docs/messaging/compliance/a2p-10dlc/troubleshooting-a2p-brands/troubleshooting-and-rectifying-a2p-standardlvs-brands)
* [A2P 10DLC Brand 2FA Verification Resource](/docs/messaging/api/brand-2fa-verify)
* [Gather the required business information for A2P 10DLC](/docs/messaging/compliance/a2p-10dlc/collect-business-info)