UNITED STATES (US)

Twilio recommends sending application-to-person (A2P) traffic over short codes for optimal delivery results. Messages sent over over long codes are subject to carrier filtering because A2P traffic is not permitted over US long codes. Twilio does not definitively know how many messages can be sent from a long code before a user can expect to hit a filter. However, we recommend following the guidelines mentioned in Messaging Principals and Basic Practices published by CTIA in Jan. 2017, where CTIA suggests that application-to-peer (A2P) messaging that's "consistent with typical human operation" should be expected to be deliverable across the messaging ecosystem. Some key attributes of typical human operation include: - Throughput: 15-60 messages per minute - Unique Recipients: 200 unique recipients per day The euro symbol (€) is not supported; avoid using this character in message submission toward the United States.

Twilio strongly encourages customers to review proposed use cases with qualified legal counsel to make sure that they comply with all applicable laws. The following are some general best practices:

1. Get opt-in consent from each end user before sending any communication to them, particular for marketing or other non-essential communications.
2. Only communicate during an end user's daytime hours unless it is urgent.
3. SMS campaigns should support HELP/STOP messages, and similar messages, in the end user's local language.
4. Do not contact end users on do-not-call or do-not-disturb registries.