Overview
When sending SMS in Mexico, recipients may sometimes see a different number than the one listed in your Phone Numbers tab. This is not a system error but rather a result of local carrier regulations and anti-spam policies. Understanding these rules is essential to avoid confusion and ensure compliance.
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
There is no official regulation stating “nine texts in two minutes,” but this reflects carrier anti-spam logic.
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.
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.