Testing SMS With the Shared Test Phone

Every Blocx account can send outbound SMS from a shared test phone number without first registering a 10DLC brand, getting a campaign approved, or buying a number. It's the fastest way to wire up the API end-to-end before you have your real sender configured.

What's different about the test phone

	Test phone	Your own number
Brand + campaign required	No	Yes
Number purchase required	No	Yes
Cost	Free	Per-segment
Rate limit	Tight — see below	Account default
Content restriction	Body must start with `[Otter]`	None
Inbound replies	Not supported	Delivered via webhook
Production traffic	No	Yes

The test phone is a sandbox. Use it to verify the request shape, your API key, your webhook signature handling, and your delivery-receipt plumbing — then switch your from to a real number when you go live.

How to use it

The shared test number is +1 307 999 9302. Set it as the from and start the message with [Otter]:

curl -X POST https://api.otterblocx.com/messaging/send \
  -H "x-access-key-id: $BLOCX_ACCESS_KEY_ID" \
  -H "x-secret-access-key: $BLOCX_SECRET_ACCESS_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "from": "+13079999302",
    "to":   "+15557654321",
    "body": "[Otter] hello from my new integration",
    "type": "SMS"
  }'

Response (202 Accepted) includes "test": true so you can tell test sends apart in your own logs:

{
  "messageId": "msg_...",
  "type": "SMS",
  "status": "QUEUED",
  "to":   "+15557654321",
  "from": "+13079999302",
  "test": true
}

Test sends flow through the same queue, the same carrier, and the same webhook contract as real sends — message.sent, message.delivered, and message.failed fire normally — so your integration code does not need to special-case them.

Rules

[Otter] prefix is required. Sends without it return 400 with code: "test_prefix_required". The prefix lets recipients identify test traffic at a glance.
Heavy rate limit. Default caps are 5 per minute, 30 per hour, 100 per day per account. Hitting any window returns 429 with code: "test_rate_limited". These are tighter than your normal account quota and cannot be raised; the test phone is for testing.
Outbound only. Replies to the test phone are dropped. If you need to handle inbound SMS, provision a real number — see Buying Phone Numbers.
No billing. Test sends do not draw from your balance and do not count toward your monthly included quota.

When to graduate to a real number

Switch as soon as you need any of:

to send to your own customers (not test handsets you control),
inbound SMS,
volume above the test phone's daily cap,
compliance with your brand and opt-in language on real traffic.

Run through Registering a 10DLC Brand → Creating a 10DLC Campaign → Buying Phone Numbers → Sending Your First SMS. Then replace the test number in your from with your provisioned number — no other code changes are required.

Testing SMS With the Shared Test Phone

What's different about the test phone

How to use it

Rules

When to graduate to a real number

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