Troubleshooting: SMS OTPs to Users in China Are Not Delivered

Version Affected: All
 
 

Overview

One-Time Passcodes (OTPs) sent via SMS to mobile devices in China may not be delivered. Since October 2026, Chinese mobile carriers have been rejecting a much larger share of SMS OTPs.

Cause

China blocks a large amount of SMS traffic that originates from outside the country. Chinese regulations have recently tightened: carriers now only accept SMS OTPs whose signature (the bracketed sender name at the start of the message) is officially registered in China to the sending organization's business entity.

A signature that is not officially registered — including a company name added in brackets to the SMS OTP message, or the [SecureAuth] prefix that earlier versions of this article recommended — causes the message to be rejected.

Resolution:

Register an official Chinese SMS signature for your organization's business entity in China. To start the registration process, contact SecureAuth Support. Support will also confirm how the registered signature should appear in your SMS OTP message once registration is complete.

Until a signature is registered, use the workaround below. Alternatively, have affected users switch to another MFA method that does not rely on SMS, such as the SecureAuth Authenticate app or another TOTP authenticator app.

Workaround:

Remove any signature from the SMS OTP message. With no signature in the message, SecureAuth's telephony partner applies its own generic signature to SMS OTPs sent to Chinese numbers. This is a temporary measure and is not guaranteed long term — some messages may still fail to deliver.

See How To: Change SMS OTP Verbiage for the general verbiage-editing procedure. For this specific case:

1. Go to the realm that sends the SMS and open the Overview tab > Content and Localization > Verbiage Editor.
2. Search for the setting onetimepasswordsms3provider_regcode.
3. Remove the signature from the start of the value — both the name and its brackets. For example, change [Company Name] Your login code is {0}. to Your login code is {0}.
4. Save the change.
5. Repeat steps 2–4 for the Chinese (Simplified) and Chinese (Traditional) language files, selected from the Language File to Edit dropdown. Chinese (Simplified) is used in China, and Chinese (Traditional) is used in Taiwan, Hong Kong, and Macau. Chinese signatures use full-width brackets — for example, 【Company Name】 — so remove the name and these brackets in the same way.
6. Repeat for every realm that sends SMS OTPs, then test.

SecureAuth Knowledge Base Articles provide information based on specific use cases and may not apply to all appliances or configurations. Be advised that these instructions could cause harm to the environment if not followed correctly or if they do not apply to the current use case.

Customers are responsible for their own due diligence prior to utilizing this information and agree that SecureAuth is not liable for any issues caused by misconfiguration directly or indirectly related to SecureAuth products.