SMS Troubleshooting
Last updated May 20, 2024
SMS delivery failures
Outbound message via SMS is attempted to send through mobile carrier may fail if the recipient cannot be reached in 3 days.
Possible Causes
- The destination handset you are trying to reach is switched off or otherwise unavailable.
- The device you are trying to reach does not have sufficient signal
- The device cannot receive SMS (for example, the phone number belongs to a landline)
- There is an issue with the mobile carrier
Full description on Twilio documentation.
If you are sending an attachment via an MMS, each carrier has a limit on size of data you can send. Here are these limits
| Carrier | Long Code | Toll Free | Short code |
| AT&T | 1.0 MB | 0.6 MB | 0.6 MB |
| Sprint | 1.5 MB | 0.6 MB | 1.0 MB |
| T-Mobile | 1.5 MB | 0.6 MB | 1.0 MB |
| Verizon | 1.0 MB | 0.6 MB | 1.2 MB |
We use Twilio to send the SMS and it internally will try to compress any image attachments. Twilio has a limit of 5 MB data size, if SMS contains payload larger than 5MB, it will give error code (11751). If payload is of any other type than image (which it won't be able to compress_ and bigger than the carrier limit, Twilio will return error code (30019).
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