Skip to main content

Documentation Index

Fetch the complete documentation index at: https://docs.hologram.io/llms.txt

Use this file to discover all available pages before exploring further.

​
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.

AT command reference and troubleshooting cellular modules

AT command reference and troubleshooting cellular modules