SMS not sending
Tell apart an inbound firewall block from an outbound delivery failure, and read the exact reason a text did not go out.
For reps · Updated Sep 23, 2026
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“SMS not sending” usually means one of two different things happened. Telling them apart first saves time, since the fix for each is different.
Note: The SMS firewall only affects texts coming in. It cannot be the reason an outbound text you sent failed to go out. If a text you sent never arrived, look at delivery reasons below, not the firewall.
Is this an inbound block, or an outbound failure?
- A text never arrived from a customer. That is the SMS firewall filtering an inbound message. See SMS firewall: block and allow lists and check the quarantine list.
- A text you sent never reached the customer. That is an outbound delivery failure. Read on.
Reading an outbound failure
Settings, then the Texting tab, then the Failed texts card, shows the plain-English reason next to each failed message:
| Category | What it means |
|---|---|
| Blocked by a carrier | The carrier filtered or blocked the message |
| Number not registered for texting | Business texting registration is missing or incomplete for the sending number |
| Landlines | The destination cannot receive texts (it’s a landline) |
| Opted out | The recipient has opted out of texts from you |
| Message content | The message content triggered a carrier content filter |
| Sending limits | A carrier-imposed sending limit was hit |
| Wrong number or setup | The number or its configuration has a problem |
| Temporary problems | A short-lived carrier issue, often resolves on retry |
| Unknown | The carrier did not return a reason Phone Clover can categorize |
Warning: If you try to text a contact who has already opted out, Phone Clover stops the send before it even reaches the carrier, since it already knows that number opted out.
Common causes, in order of likelihood
1. A2P 10DLC registration is missing or incomplete
Most “Blocked by a carrier” and “Number not registered for texting” failures trace back here. US carriers require your business to be registered before they will deliver texts from a local number. Check Settings, then the Texting tab, then Business texting registration, and look for a Registered chip next to the sending number. See Register for A2P 10DLC.
2. The number was never text-enabled
If the number is a number you brought over with Hosted SMS rather than one bought through Phone Clover, texting only turns on once that request clears review. Check its status on the Numbers tab. A number stuck in review, or one where the letter of authorization was rejected, cannot send texts yet. See Text from your existing business number without porting.
3. The destination is a landline
Turn on Skip landlines in the Failed texts card so Phone Clover checks a number before attempting to text it, instead of finding out after a failed send. See Why texts fail and what the reasons mean.
4. The recipient opted out
Once a contact opts out, Phone Clover will not send them another text from this channel. This is not a bug to work around; it reflects their opt-out.
5. A temporary carrier issue
Turn on Retry from another number so a short-lived problem on one number does not keep failing your sends. It automatically resends from another number you own.
6. The number is unhealthy
A number that carriers have started flagging can see worse delivery even before it shows an outright failure. Check Number health radar for that number’s Delivered and Spam trend.
Troubleshooting checklist
- Open Settings → Texting → Failed texts and read the category next to the failed message.
- If it says Blocked by a carrier or Number not registered for texting, check A2P 10DLC registration status first.
- If it says Landlines, confirm the destination number type, or turn on Skip landlines.
- If it says Opted out, stop; do not attempt to text that contact again from this channel.
- If it says Temporary problems, turn on Retry from another number and try again.
- If failures keep happening on one specific number regardless of the category, check Number health radar for that number.