Understand SMS delivery statuses
- Sending from a Hologram device: “Delivered” means Hologram delivered the SMS to the receiver’s network; last-mile delivery to the device is not guaranteed.
- Sending to a Hologram device: “Delivered” means the sender’s network delivered to the network your device is attached to; last-mile depends on that network and device state.
Note: Charges apply for a successful send from Hologram, even if the end device does not receive the SMS.
Common issues
Carrier blocks international SMS
Some carriers block international SMS by default (Hologram uses global, non-domestic numbers). Ask the carrier to allow messages from international numbers (for example, +882 or +999).Cat-M1 SMS maturity
On some networks, SMS over Cat-M1 may be delayed or require both sender and receiver to be on the same Cat-M1 network.Incorrect SMSC routing
Misconfigured SMSC mappings on either network can prevent delivery. These mappings are controlled by carriers.Additional troubleshooting
1
Check Hologram status
Confirm there are no incidents affecting SMS or API.
Status page
2
Verify device state and signal
Ensure both devices are powered and have adequate coverage.
3
Test with a different receiver
If sending from a Hologram device, test to another device (ideally on the same carrier) and confirm it receives SMS.
4
Read SMS via AT commands
Use
AT+CMGL or the device’s documented command set to read stored SMS.Related guides
AT command reference and troubleshooting cellular modules
AT command reference and troubleshooting cellular modules