TABLE OF CONTENTS
Key Points
1. Sender ID Behavior in Mexico
- Mobile carriers in Mexico have strict regulations on SMS sender IDs.
- Messages sent from long codes (regular phone numbers) may have their sender ID overwritten or replaced with a random or generic number, particularly for application-to-person (A2P) traffic.
- AT&T Mexico is somewhat unique—it sometimes allows person-to-person (P2P) SMS from regular numbers, but this is not guaranteed across all scenarios or volumes.
2. Message Volume and Sender ID Changes
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There is no official regulation stating “nine texts in two minutes,” but this reflects carrier anti-spam logic.
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If a phone number sends high volumes of SMS in a short time, carriers may:
- Reclassify the traffic as A2P.
- Automatically rewrite the sender ID.
- In some cases, block the messages altogether.
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These measures are in place to comply with local spam and regulatory requirements.
3. Why Recipients See a Different Number
- If you send SMS from a regular number and exceed allowed patterns or volume, the carrier may override your sender ID.
- This results in recipients seeing a different number or a generic sender ID, even though you sent it from your configured number.
4. Default Sender ID Registration
- If you have a registered Sender ID in Mexico, Twilio will use it consistently.
- If you do not, the default carrier behavior applies, which may include sender ID changes.
Suggested Solution
To ensure consistent SMS delivery in Mexico:
- Register a Sender ID approved for Mexico.
- Or, use a short code or another compliant messaging channel designed for A2P traffic.
These options guarantee that messages display a consistent sender ID and comply fully with local carrier rules.
Final Note
If your recipients in Mexico are seeing a different number than expected, it is due to carrier enforcement—not a misconfiguration in your account or Twilio. This behavior is beyond your direct control unless you register an official Sender ID or adopt a supported A2P channel.