SMS isn't sending

SMS delivery failures fall into a handful of categories. The reason code on the failed message tells you which one — start there.

1. Read the delivery status

Inbox → Messages → open the affected thread → click the red failed message.

You'll see:

Status: failed
Error: 30007 — Carrier filtered
Recipient carrier: T-Mobile
Sent: 2026-01-15 10:32 AM

Cross-reference the error code:

Code	Meaning	Fix
30003	Unreachable destination handset	Phone is off, out of coverage, or no longer in service. Wait or remove the number.
30004	Message blocked by recipient	They replied STOP at some point. Remove from your list.
30005	Unknown destination handset	Number is invalid or disconnected. Verify the number.
30006	Landline or unreachable carrier	Number is a landline — SMS can't deliver.
30007	Carrier filtered (spam-flagged)	See section 2 below.
30008	Unknown error	Transient; retry. If persistent, contact support.
21610	Recipient unsubscribed	They replied STOP. Honor it.

2. Carrier filtering (30007) — the big one

This is by far the most common failure. Carriers (especially T-Mobile post-merger) aggressively block business SMS that looks unverified or spammy. Fixes in order:

Confirm A2P 10DLC registration

Settings → Phone → A2P Registration. If status is anything other than Approved for the brand and campaign, your local US numbers are throttled or blocked.

Register for A2P — 5 minutes to submit, 1–7 days for approval
Without registration, ~30–60% of T-Mobile messages get filtered

Confirm toll-free verification

For toll-free numbers, Settings → Phone → click the toll-free number → Verification. Status should be Approved. If Rejected, the rejection reason explains what to fix (usually the use case description or opt-in proof).

Clean up your message content

Common spam triggers:

All caps, especially in the first line
Urgency words — FREE, CLICK NOW, LIMITED TIME, GUARANTEED
Shortened URLs (bit.ly, tinyurl) — use the full URL or a branded short domain
Unicode emoji + special characters in volume
Phone numbers without context

Compare a "good" reminder vs. a "bad" one:

✅ "Hi Sarah, this is Sunny Dental reminding you of your cleaning
   tomorrow at 2pm. Reply YES to confirm or RESCHEDULE to change."

❌ "🔥 FREE consult AVAILABLE! Click here NOW to book ⚡⚡⚡
   bit.ly/sunny-dental"

3. Toll-free number suddenly stopped delivering

Toll-free verification can be revoked if your delivery rate to T-Mobile drops below ~70% — the system assumes you're sending spam. To recover:

Reduce send volume for 48 hours
Re-submit toll-free verification with current use case
Once re-approved, ramp volume back up gradually

4. Quiet hours and rate limits

US carriers enforce quiet hours — no marketing SMS between 9pm and 8am recipient local time. Transactional messages (appointment reminders, confirmations) are exempt but err on the side of caution. We won't block your outbound, but carriers will.

Pro plan and above include a "Respect quiet hours" toggle in Settings → Messaging that queues out-of-window messages for the next allowed send time.

What's next

Register for A2P 10DLC
Send and receive SMS overview
For broader call/SMS issues see My AI isn't answering calls

Frequently asked questions

How do I see why a message failed?

Open the thread in Inbox → Messages. Click the failed message — you'll see status (failed, undelivered) and a reason code (e.g., "30007 — Carrier filtered", "30005 — Unknown destination handset"). The reason guides the fix.

My toll-free number was working but stopped delivering

Toll-free verification can be revoked if delivery rates spike above carrier thresholds. Check Settings → Phone → your toll-free number → Verification status. If it shows Rejected or Pending, re-submit verification.

Carrier filtered (30007) keeps showing up

This means a carrier (usually T-Mobile/Sprint) flagged your message as spam-like. Top causes: no A2P 10DLC registration, message content with words like "free", "click here", "guaranteed", or sending to recipients who didn't opt in.

Some recipients get my texts, others don't

Almost always carrier-specific filtering. Verify each affected recipient's carrier, check our A2P registration status, and try a plainer message body without urgency words or shortened links.