US long code numbers are restricted to sending 10 messages per minute for any single long code. If you require faster throughput then you must purchase more long codes. If you ignore these recommendations, then the mobile operators will block your numbers.
By default, your overall Telnyx portal account is limited to sending 1 message / second. If you require a higher limit, please reach out to email@example.com via email, and we can talk about raising your message rate limit.
Please note: If you create messages at faster rate then Telnyx will queue up the messages and send them at a reduced rate. Messages that are queued (and not yet sent) will not appear in the MDR reports.
For more information see our article on Long Code Deliverability Best Practices.