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Does Duo’s SMS and phone callback service work in countries outside the United States?
As noted by an “N/A” on the telephony rate card, Duo’s system doesn’t always know a route or telephony credit rate for both SMS and phone callback in all countries. Duo may know a route for phone calls but not SMS, or vice versa. If a device with such a number is enrolled in Duo, phone callback or SMS won’t show up as an option in the Duo Prompt. Duo’s route database is based on all its telephony providers and support may be added for more countries as they become available.
Some countries and regions outside of North America and Europe have relatively unreliable telephony infrastructure. This can lead to inconsistent phone callback and SMS authentication experiences. In these circumstances, we recommend considering using alternative authentication mechanisms such as Duo Push, generating passcodes in Duo Mobile, phone callback, or hardware tokens. Another consideration to keep in mind with these countries and regions is the high cost of telephony delivery.