US MNO Wholesale · US Local Numbers · Two-Way SMS API
Send & receive SMS
that actually arrives.
VoIP DIDs from Twilio, UCaaS, and CRM platforms often carry C-level STIR/SHAKEN attestation, making them more likely to be flagged, silently dropped by major U.S. carriers, or blocked by bank fraud filters and government portals.
Spenza numbers are provisioned through a US mobile operator wholesale network with full A-level attestation, helping messages get delivered in both directions.
The Deliverability Gap
VoIP DIDs vs. Local Numbers
Not all phone numbers are equal. The DID source determines whether your message is delivered, filtered, or silently blocked.
VoIP DIDs (Twilio, UCaaS, CRM)
- Numbers sourced from VoIP aggregators, not licensed MNOs
- Shared DID ranges flagged in carrier spam databases
- More likely to receive lower STIR/SHAKEN attestation
- Filtered at the SMS firewall layer — no delivery, no error code
- Rejected by bank KYC flows and government OTP endpoints
- Flagged by enterprise security policies in SaaS platforms
- No MSISDN-level trust; treated as bulk sender by default
- Inbound bank OTPs & 2FA codes blocked, users never receive them
- Numbers provisioned under wholesale MNO contracts
- Dedicated MSISDN ranges not shared with other platforms
- Pass operator-level trust validation on delivery
- Accepted by government and enterprise messaging endpoints
- Full two-way SMS: receive inbound replies on the same number
- Designed to support bank OTP and verification flows
- Number is yours — port out to any carrier at any time
- Upgrade to data eSIM plan with native voice & SMS on the same number
Infrastructure
Direct from the network
Spenza provisions numbers through a direct wholesale relationship with a US mobile operator — not through a VoIP overlay, reseller chain, or shared number pool.
- 01 · PROVISION
Dedicated local numbers
Get a real geographic or national number via API, provisioned on live MNO infrastructure, dedicated to your account. Choose by country, prefix, or area code.
- 02 · SEND & RECEIVE
Two-way SMS API
POST to send, receive inbound via webhook. Replies land on the same number. Supports Unicode, concatenation, and delivery receipts with real carrier DLRs.
- 03 · TRUST SIGNAL
MNO-level reputation
Numbers originate from US mobile operator infrastructure and carry A-level STIR/SHAKEN attestation, giving carriers stronger trust signals than typical VoIP DIDs.
- 04 · GROW
Upgrade to full eSIM plan
Keep the same number. Upgrade to a data eSIM plan with native voice & SMS, or port out to any carrier.
- SMS delivery rate to bank-registered numbers
- 99.1%
- STIR/SHAKEN attestation on supported US MNO routes
- A
- Median time-to-delivery on MNO routes
- <2s
- Numbers flagged in spam databases at provisioning
- 0%
Developer API
Integrate in minutes
REST API with webhooks. Familiar to integrate, built for reliable delivery.
# Send an SMS from your Spenza local number curl -X POST 'https://api.spenza.io/v1/messages' \ -H 'Authorization: Bearer sk_live_••••••••' \ -H 'Content-Type: application/json' \ -d '{ "from": "+1 415 555 0192", "to": "+1 212 555 0147", "text": "Your OTP is 847291. Valid for 5 minutes.", "route": "mno_direct" }' # Response { "id": "msg_01J8xkp3q7mHnNvTdF2CG", "status": "queued", "route": "mno_direct", "network": "T-Mobile US", "segments": 1 }
# Inbound webhook — POST to your endpoint # Configure at: dashboard.spenza.io → Numbers → Webhooks POST https://your-app.com/sms/inbound { "event": "message.inbound", "id": "msg_01J8ykr9p4nXoQwTeG3DH", "to": "+1 415 555 0192", "from": "+1 212 555 0147", "text": "Yes, confirm appointment", "received_at": "2024-09-18T16:42:01Z", "network": "T-Mobile US" } # Respond with HTTP 200 to acknowledge
# Provision a new local number curl -X POST 'https://api.spenza.io/v1/numbers' \ -H 'Authorization: Bearer sk_live_••••••••' \ -d '{ "country": "US", "type": "local", "capabilities": ["sms", "voice"] }' { "number": "+1 646 555 0188", "country": "US", "mno": "T-Mobile (wholesale)", "type": "local", "spam_score": 0.0, "status": "active" }
Why It Matters
Where VoIP numbers get filtered
Spenza numbers are backed by US mobile operator infrastructure, helping them pass trust checks that can cause VoIP DIDs to be filtered or rejected.
Banks & Financial Services
Get OTPs and verification messages through
Bank-linked mobile flows often apply strict anti-fraud checks. VoIP ranges can be filtered, while US MNO-backed numbers carry stronger mobile-network trust signals.
Government & Federal Portals
Work with verification-sensitive services
Government identity and verification flows may require a recognized US mobile number. MNO-backed numbers are better aligned with those requirements than standard VoIP DIDs.
Enterprise SaaS & CRM Inboxes
Avoid shared VoIP reputation issues
Enterprise platforms can use carrier and reputation data to filter inbound SMS. Dedicated mobile operator-backed numbers avoid the reputation risks of shared VoIP ranges.
Mobile Operators & A2P Firewalls
Pass carrier-level trust checks
US operators enforce messaging and identity controls at the network level. MNO-backed numbers originate from mobile-network infrastructure rather than a VoIP layer.
Number Ownership
Your number. Your control.
Unlike VoIP DIDs drawn from shared pools, Spenza numbers are assigned directly to your account, with full portability and a clear path to broader mobile connectivity.
You own the number
Dedicated to your account
Each number is assigned exclusively to you — no shared pool, no reuse across customers, and less risk of inheriting another sender’s reputation history.
Port out anytime
Take your number with you
Your number is portable under standard US number-porting rules, so you can move it to another supported carrier or account when needed.
Upgrade to eSIM data
Keep the number as you expand
Use the same number as you move from messaging to a full mobile plan with voice, SMS, and data on supported eSIM devices.
Built For
Use cases that need real delivery
Authentication & OTP
Deliver verification codes reliably
Send one-time passwords and authentication messages to users who may otherwise be blocked or filtered when using VoIP-based numbers.
Notifications
Make critical notifications reach users
Use local mobile-backed numbers for delivery, payment, appointment, and account alerts that need to arrive on time.
Sales & Marketing SMS
Use local numbers for customer outreach
Replace VoIP or CRM-issued DIDs with dedicated local numbers that carry stronger mobile-network trust signals.
Two-Way Customer Support
Keep conversations on one number
Receive replies on the same local number. No VoIP relay, no intermediate carrier hop — direct MNO path.
KYC & Compliance Flows
Support verification-sensitive workflows
Use MNO-backed numbers for SMS-based identity, onboarding, and compliance flows where number type and trust signals matter.
UCaaS & CRM Integration
Keep your platform. Upgrade the number.
Continue using your existing UCaaS or CRM workflow while replacing the underlying VoIP DID with a Spenza local number.
Get Started
Start with a real local number.
Provision a number in under 60 seconds. No commitment, no shared pool, no VoIP relay.