Updated: September 2025
This guide outlines phone related error codes encountered in the People tab and in the Delivery Errors bucket of Mustr Details. Use this to quickly understand what the error means.
SMS Opt-Out
SMS Opt-Out
Meaning: The recipient has opted out of receiving SMS messages.
Common Causes:
User replied with STOP, CANCEL, or similar to a previous SMS.
User preferences or system removed SMS consent.
Recommended Action: Ask the user to text START to your number to re-subscribe (if applicable).
Unreachable Destination Handset
Unreachable Destination Handset
Meaning: The recipient's device is not reachable via SMS.
Common Causes:
Phone is out of coverage.
SIM card deactivated or removed.
Carrier issues.
Recommended Action:
Try again later.
If the issue persists, verify the number with the user or check with the carrier.
Number OOS (Out of Service)
Number OOS (Out of Service)
Meaning: The phone number is currently out of service.
Common Causes:
Disconnected or deactivated number.
Number does not exist.
Recommended Action:
Confirm the number with the user.
Ask the user to update their contact information.
Do not retry to send again until the number is verified.
Member Phone Off
Member Phone Off
Meaning: The recipient’s phone is turned off or out of battery.
Common Causes:
Device is powered down.
No network connection at time of sending.
Recommended Action:
No immediate action required.
The message may be delivered once the phone is turned back on.
If urgent, contact the user through another channel.