# Blocx — Full Reference for LLMs

## Blocx vs. Twilio
- https://otterblocx.com/twilio-alternative compares SMS base rates, plan-specific support, fees, registration, and migration. Starter has docs and tickets without human support; Scale and Volume include private developer-team Slack. Base-rate differences are not total-bill savings. Twilio sources were checked October 26, 2026.

> Programmable messaging API. SMS, MMS, RCS, Email, and Telegram — all live under a single REST API. Built and operated by OtterBlocx, LLC (Cheyenne, WY).

## Company
- Product name: Blocx
- Legal entity: OtterBlocx, LLC
- Headquarters: Cheyenne, Wyoming, United States
- Brand: Ink, Paper, Orange. Unbounded headlines, Geist reading text and Geist Mono for code and the lowercase wordmark. Messaging-first examples and plan-qualified pricing.

## Getting Started Guide

- https://otterblocx.com/getting-started — A dedicated guide for preparing a US 10DLC brand, campaign and consent flow; choosing a sender; installing the official SDK; testing outbound SMS/MMS, signed inbound and delivery webhooks, and launch controls.
- Existing providers, CSPs and software platforms should discuss number portability, campaign reuse, account structure, authorization, costs and cutover planning with Blocx. The guide does not promise immediate, fee-free or disruption-free migration.
- Official SDK: https://otterblocx.com/sdk. Current API documentation: https://api.otterblocx.com/docs. Integration and migration questions: https://otterblocx.com/contact.

## What Blocx Does
Blocx provides one REST API for sending and receiving messages across its live messaging channels:
- SMS (Live)
- MMS (Live)
- Email — transactional and marketing (Live)
- Telegram (Live)
- RCS (Live)

The official JavaScript/TypeScript SDK is the downloadable npm package `@otterlabs/blocx`. It supports messaging, email, and verification; it does not provide Voice support.

## Voice Services
- https://otterblocx.com/voice describes separate Voice services from OtterBlocx, LLC: Voice over Internet Protocol (VoIP), voicemail, call routing, 2FA via AI caller, and a voice dialer.
- Contact OtterBlocx at https://otterblocx.com/contact for access.
- These Voice services are separate from the messaging channels and are not channels on the Verify API. Do not infer unlisted API endpoints or Voice SDK support.

It is positioned as a Twilio-style infrastructure provider, with a stronger emphasis on consolidating channels behind a single API surface and offering AI-assisted message flow generation.

## Core Capabilities
- Monthly spend caps are available on all plans: Starter, Scale, and Volume. Sending stops when the monthly cap is reached, including compromised-key and runaway-loop traffic.
- Blocx blocks duplicate sends at the API level to prevent duplicate texts and duplicate charges. Do not infer a detection algorithm or time window.
- Blocx platform rates never increase and can decrease with scale. Carriers set their own passthrough fees, which can change.
- Starter provides standard throughput, docs, and tickets with no human support. Scale and Volume get highest priority on the Blocx sending queue and a private Slack channel with the Blocx dev team.
- 10DLC throughput limits are set by carriers per campaign. Plan priority applies to the Blocx platform queue.
- Restricted-vertical senders on Scale get a dedicated compliance contact to review their use case and keep messaging within carrier rules. Carriers make the final approval decision, so approval is not guaranteed.
- Unified REST API. SMS, MMS, RCS, Email, and Telegram are all live and ship through the same envelope.
- Verified sending domains with dedicated IP support on paid plans.
- Marketing email and campaign tooling included.
- 2FA / verification API priced per successful verify.
- Number lookup and number management.
- Priority routing and automated failover between channels.
- AI-assisted flow generation: describe communication flows in natural language, generate webhooks, routing logic, and API calls.
- Sandbox environment for development and testing.

## Switch to Blocx
- https://otterblocx.com/switch consolidates SMS, MMS, RCS, Email, and Telegram behind one API, one delivery-receipt surface, and configurable channel failover.

## Blocx Verify vs Twilio Verify
- https://otterblocx.com/verify-vs-twilio
- Blocx Verify costs $0.035 per successful verification on Starter and Scale, includes SMS or email delivery, and does not bill failed or abandoned attempts.
- Twilio Verify is compared at $0.05 per successful verification plus standard channel charges, or roughly $0.058 total for US SMS. The page also explains the supplied push-rejection billing caveat.
- The page uses standard Scale rates throughout, with a $1,000/month annual commitment starting on day 31 after the first 30 days with no minimum.

## Solutions
These are customer integration use cases, not claims of prebuilt vertical applications or automatic storefront and scheduling integrations.
- E-commerce: https://otterblocx.com/solutions/ecommerce
- SaaS: https://otterblocx.com/solutions/saas
- Financial Services: https://otterblocx.com/solutions/financial-services
- Healthcare: https://otterblocx.com/solutions/healthcare
- SHAFT: https://otterblocx.com/solutions/shaft
- Authentication: https://otterblocx.com/solutions/authentication
- Order Notifications: https://otterblocx.com/solutions/order-notifications
- Cart Recovery: https://otterblocx.com/solutions/cart-recovery
- Marketing Campaigns: https://otterblocx.com/solutions/marketing-campaigns
Customer systems supply application events, audiences, consent, scheduling, and business decisions. Blocx supplies messaging delivery through its documented interfaces. Example messages are illustrative, not live traffic or working verification codes.
Healthcare and financial-services pages do not represent HIPAA certification, a BAA, financial compliance certification, or permission to send sensitive data. Customers must review their own requirements.
Authentication examples refer to the SMS/email messaging Verify service. Voice and AI-caller services remain separate offerings. Plan, carrier, and opt-out requirements still apply.

SHAFT industry examples cover eligible firearms, cigar/tobacco, and alcohol businesses on Scale, with a dedicated compliance contact. Telegram is a second channel alongside Email for eligible vape, cannabis (weed), and THC communications that cannot be sent over SMS. Telegram eligibility does not authorize SMS traffic or remove Telegram policies and Blocx review. Starter does not support restricted verticals. Customers remain responsible for lawful products, licensing, age and jurisdiction restrictions, consent, and opt-outs. Approval is not guaranteed. The 10DLC approval-time guarantee does not apply to SHAFT companies.

## Plans

Three ways to buy. Published channel rate cards use Scale-plan rates unless Starter is explicitly labeled.

- Monthly spend caps are available on Starter, Scale, and Volume. Set a monthly spend cap. Hit it and sending stops.
- 10DLC throughput limits are set by carriers per campaign. Plan priority applies to the Blocx platform queue.
- Carriers set their own fees and pass them through. Those can change. Our rate stays locked.
- Blocx blocks duplicate sends at the API level, so a retry loop or integration bug doesn't text your customers twice or charge you twice. Technical detection rules and the time window remain unspecified.
- Restricted-vertical senders on Scale get a dedicated compliance contact who reviews your use case and keeps your messaging within carrier rules. Carriers make the final approval decision, so approval is not guaranteed.

### Starter — Self-serve with $25 in welcome credit. The paid Starter plan is $49/month credited toward usage.
- SMS: $0.0065/segment
- Email: $0.001/email
- 1 sending domain · 1 API key
- REST API, dashboard & sandbox
- Monthly spend caps
- Standard throughput
- Docs and tickets. No human support.
- Not included: MMS, RCS & Telegram
- Not included: SHAFT & restricted verticals

Every new account gets $25 in credit to cover its first brand, campaign, phone numbers and messages. Carrier registration and channel eligibility requirements still apply. The welcome credit is separate from Scale's 30-day no-minimum ramp.

### Scale — $1,000/month minimum platform spend on an annual contract. The minimum starts on day 31; no minimum for the first 30 days. Signup starts with a call. Required tier for SHAFT and other restricted verticals.
- Everything in Starter
- SMS from $0.0045 · MMS from $0.0135 · Email $0.0002
- MMS, RCS & Telegram unlocked
- Verify (2FA): $0.035 flat
- 10DLC, toll-free & short code setup
- First 30 days with no minimum
- Unlimited domains & API keys
- 1:1 onboarding
- Monthly spend caps
- Highest priority on the Blocx sending queue
- Private Slack channel with the Blocx dev team
- Every channel included: SMS, MMS, RCS, Email, Telegram, and Verify (2FA)
- 10DLC brand & campaign registration included; toll-free and short code provisioning handled in-app
- Dedicated sending IP available as a quoted add-on
- Sandbox unlimited
- Knowledge base & community access

Every channel and route type at the published rate card; usage across all channels counts toward the commitment. Published channel rate cards use Scale rates unless Starter is explicitly labeled.

### Volume — From $5,000/month, with four published commitment levels; contact sales.
- Everything in Scale
- Volume-based rate discounts
- 10DLC SMS as low as $0.0026
- Four published commitment levels
- Dedicated routing
- Monthly strategy call
- SLA-backed uptime guarantee
- Monthly spend caps
- Highest priority on the Blocx sending queue
- Private Slack channel with the Blocx dev team
- Dedicated sending IP included
- Priority response SLA
- Volume-friendly invoicing and net-30 terms

Rates negotiated on your traffic profile.

## 10DLC approval guarantee
48-hour 10DLC approval guarantee. To qualify, you must complete a one-on-one with a Blocx 10DLC expert, have that expert approve your submission before carriers receive it, and follow the expert's advice. The guarantee does not apply to SHAFT companies.

## Usage Rates (published rate card; Volume plan rates are custom)

### Email
- $0.0002 per email.
- Unlimited verified domains included.

### SMS
- 10DLC $0.0045, toll-free $0.0055, short code $0.007 per message + carrier fee.
- Carrier fees passed through at cost, line-itemed per carrier on every accepted message.

### MMS
- 10DLC $0.0135, toll-free $0.016, short code $0.018 per message + carrier fee.
- Carrier fees passed through at cost.

### Telegram
- Flat $0.0045 per message in either direction (sent or received).
- No carrier fees.

### RCS
- $0.0135 per RCS message.
- One-time $1,000 setup fee for Verified Business Sender registration.
- Automatic SMS fallback when unsupported.

### 2FA Verification
- $0.035 per successful verification. Failed attempts free; sandbox unlimited.

## Phone Numbers & Short Codes

### Long Codes (10DLC)
- Local US 10-digit long codes for app-to-person (A2P) SMS traffic.
- Provisioned from the dashboard; per-number monthly carrier fee passed through at cost.
- Brand and campaign registration with The Campaign Registry (TCR) handled in-app.
- Toll-free SMS numbers also available with the same workflow.
- International local long codes available on request.

### Short Codes (US, dedicated)
- Random short code (carrier-assigned 5–6 digits): $1,000 one-time setup fee + $2,700 per quarter lease. Billed quarterly in advance.
- Vanity short code (your choice of digits): quoted per request — contact sales.
- International short codes: quoted per request.
- Higher throughput tier than standard 10DLC long codes; final throughput set during the carrier approval process.
- Setup fee covers carrier provisioning and CTIA program brief review.

## Developer Surface
- REST API with consistent envelope across channels.
- Official JavaScript/TypeScript SDK: npm package `@otterlabs/blocx`, supporting messaging, email, and verification.
- Install: `npm install @otterlabs/blocx`
- npm package: https://www.npmjs.com/package/@otterlabs/blocx
- Verified v1.1.0 release archive: https://registry.npmjs.org/@otterlabs/blocx/-/blocx-1.1.0.tgz
- No other official SDK language packages are listed here; Voice SDK support is not included.
- Comprehensive, versioned API docs with interactive examples — live at https://api.otterblocx.com/docs (OpenAPI 3.1, rendered with Scalar).
- Sandbox environment for testing before going live.
- Custom dashboard for API keys, usage, analytics.

## Compliance & Legal
- Privacy policy covers GDPR (EU/EEA), CCPA/CPRA (California), data retention, international transfers, and user rights.
- Terms of service available at /terms.
- Contact for all inquiries (privacy, security, legal, sales, partnerships): https://otterblocx.com/contact

## Conversion Landing Pages (paid acquisition only)
- https://otterblocx.com/lp/sms — Single-CTA landing page for SMS. Headline: "A US SMS API engineers ship the same day." Stripped header, repeats the "Get API Keys" CTA, surfaces canonical SMS rates (10DLC $0.0045/msg, toll-free $0.0055, short code $0.007 — all + carrier passthrough), links to /messaging/pricing for full tables. Used as the destination for X (Twitter) Ads SMS campaigns.
- https://otterblocx.com/lp/email — Single-CTA landing page for Email. Headline: "Transactional + marketing email at $0.0002 — flat." Repeats the "Start Sending" CTA, surfaces the canonical $0.0002/email flat rate — one published rate — links to /email/pricing.
- https://otterblocx.com/lp/verify — Single-CTA landing page for Verify. Headline: "2FA you only pay for when it works." Repeats the "Get Verify Keys" CTA, surfaces the canonical $0.035 per successful verify with failed attempts free, links to /verify#pricing.
- All three LPs use the attribution helper to forward UTMs and twclid to app.otterblocx.com on every CTA, and fire the X Pixel Signup conversion event on click.

## Analytics & Tracking
- The marketing site runs a single advertising pixel: X (Twitter) Ads conversion pixel rcc0i.
- Cookie consent: in the EU/EEA the pixel does not load until the visitor accepts the consent banner (persisted in localStorage["blocx-consent"]). Outside the EU/EEA the pixel loads on first paint.
- SPA events fired client-side: PageView on every route change; ViewContent on /sms, /mms, /email, /verify, /messaging/pricing, /pricing, and the three /lp/* pages; Signup conversion on every CTA targeting app.otterblocx.com; Lead conversion on successful contact-form submission.
- All conversion events include a per-fire conversion_id and a SHA-256-hashed, lowercased email when one is available client-side.

## Blog Posts (most recent first)
- https://otterblocx.com/blog/preventing-duplicate-messages-idempotency-keys — Prevent duplicate SMS and MMS (October 26, 2026). Author: Ali Gasimzade, Senior Engineer. Why backend retries cause duplicate texts, the optional SMS/MMS Idempotency-Key contract, safe replay and error handling, and customer-first protection against unnecessary sends.
- https://otterblocx.com/blog/blocx-contacts-smarter-messaging — Blocx Contacts: profiles that learn with every send (October 26, 2026). Author: Ali Gasimzade, Senior Engineer. Automatic contact creation on first send, channel availability and defaults, delivery-history learning, and API-connected customer profiles with opt-in context.
- https://otterblocx.com/blog/build-a-marketing-suite-inside-your-pos — Build a marketing suite inside your POS (published October 1, 2026; pricing and resources reviewed October 26, 2026). Author: Ali Gasimzade, Senior Engineer. SMS/email marketing as recurring POS software revenue beyond payment processing, with merchant workflows, cost allocation, account-structure considerations, consent and Blocx SDK/API resources.
- https://otterblocx.com/blog/give-your-ai-agent-a-phone-number — Give your AI agent a phone number (published September 20, 2026; resources reviewed October 26, 2026). Author: Ali Gasimzade, Senior Engineer. A five-step SMS guide covering number selection, the official SDK, AI-readable docs, secure tools, signed inbound/delivery webhooks, consent and testing. Voice services are discussed separately from the messaging SDK.
- https://otterblocx.com/blog/twilio-sms-pricing-explained-2026 — Twilio SMS pricing explained (published September 16, 2026; pricing updated October 26, 2026). Author: Ben Nelson, CEO. SMS segments, carrier fees, numbers, A2P registration, Verify pricing and a two-million-segment base-cost comparison using the qualifying Blocx Volume tier.
- https://otterblocx.com/blog/ai-text-agents-that-convert — Build AI text agents that convert (published September 1, 2026; resources reviewed October 26, 2026). Author: Ali Gasimzade, Senior Engineer. SMS delivery, concise replies, conversation state, safe handoffs and application-confirmed outcome measurement; links to the official SDK, API reference and AI-readable resources.
- https://otterblocx.com/blog/10dlc-vs-toll-free-vs-short-code — 10DLC vs. toll-free vs. short code: which number should you use? An opinionated guide to US business number strategy: start with registered 10DLC for opted-in lists under roughly 30,000, use toll-free only when a national service identity genuinely fits, and graduate to a dedicated short code when list size, burst frequency, and delivery windows justify it. Compares registration, throughput, customer perception, cost, and migration planning. Author: Ben Nelson. August 26, 2026.
- https://otterblocx.com/blog/quiet-hours-shaft-carrier-caps-compliance-playbook — Quiet hours, SHAFT, and carrier caps: the compliance playbook for text infrastructure. A builder's guide to the compliance layer above a messaging API: federal and state quiet hours, explicit consent records, account and per-number limits, T-Mobile brand-level daily caps, SHAFT content review, 10DLC registration, and enforcement risks. Includes current Blocx dashboard defaults, carrier-cap tables, and an implementation checklist. Author: Ben Nelson. August 26, 2026.
- https://otterblocx.com/blog/10dlc-use-cases-that-get-approved — 10DLC use cases that get approved: transactional, 2FA, and mixed campaigns. A field guide to registering A2P 10DLC campaigns that pass carrier/TCR review. Explains the brand→campaign structure, then gives three complete worked examples — transactional customer care, 2FA one-time passcodes, and mixed (marketing + customer communication) — each with the use case, campaign description, message flow/opt-in, opt-in/STOP/HELP keywords, auto-replies, and sample messages. Covers the six elements of a compliant opt-in consent box, the most common rejection (CTA error 806) and exactly how to fix it, and a decision table for picking the right use case. Author: Ben Nelson. June 5, 2026.
- https://otterblocx.com/blog/rotating-numbers-not-a-compliance-strategy — "Rotating numbers" is not a compliance strategy — here's what actually works. Why burning and rotating phone numbers doesn't fix deliverability: the flagged campaign registration at The Campaign Registry follows your brand/EIN, every new number inherits that liability, and swapping numbers resets your TCPA opt-in list from scratch. Includes how to pick the right number type for SaaS (short codes vs toll-free vs dedicated 10DLC) and what to do with an inherited flagged registration. Author: Ben Nelson. May 23, 2026.
- https://otterblocx.com/blog/webhooks-rest-vs-smtp-for-auth-email — Webhooks + REST > SMTP: a better way to send auth and product email. Why a REST API plus inbound webhooks beats raw SMTP for auth and product email — retries, observability, templating, and reply handling — and the narrow cases where SMTP is still the right answer. Author: Ali Gasimzade. May 12, 2026.
- https://otterblocx.com/blog/ai-agent-that-texts — Building an AI agent that texts: webhooks, tool calls, and Blocx in ~100 lines. End-to-end Node walkthrough wiring an LLM tool call to Blocx SMS and receiving inbound replies via webhook. Author: Ali Gasimzade. May 11, 2026.
- https://otterblocx.com/blog/cold-start-email-sender-reputation — Cold-start an email sender reputation: a 30-day plan for new domains. Practical SPF/DKIM/DMARC setup plus a volume-curve table from 50/day to 50k/day, provider-agnostic. Author: Ali Gasimzade. May 8, 2026.
- https://otterblocx.com/blog/supabase-auth-emails-with-blocx — Sending Supabase auth emails through Blocx: what works, what doesn't. Honest notes on the Supabase SMTP slot tradeoff plus an Edge Function pattern for non-auth product email. Author: Ali Gasimzade. May 7, 2026.
- https://otterblocx.com/blog/carrier-passthrough-fees-explained — Carrier passthrough fees, explained: why your SMS bill has two line items. A2P 10DLC primer, why Blocx itemizes carrier fees rather than blending them, and how to estimate true all-in cost at canonical rates (SMS 10DLC $0.0045 + carrier, toll-free $0.0055 + carrier, MMS 10DLC $0.0135 + carrier). Author: Ali Gasimzade. May 6, 2026.
- https://otterblocx.com/blog/transactional-email-pricing-comparison-2026 — Transactional email pricing, compared: Blocx, Resend, Postmark, SES, SendGrid. Side-by-side per-email price, free tier, and best-fit use case across the major transactional email providers in 2026. Author: Ali Gasimzade. May 5, 2026.
- https://otterblocx.com/blog/rcs-channel-agnostic-notification-layer — Now that RCS is live — how a channel-agnostic notification layer made it a one-day integration. A small envelope + registry abstraction that made adding live RCS ($0.0135/msg + $1,000 setup) a single afternoon of work. Author: Ali Gasimzade. May 4, 2026.
- https://otterblocx.com/blog/mms-in-2026-picture-instead-of-link — MMS in 2026: when to send a picture instead of a link. Three use cases (delivery proofs, appointment confirmations, marketing) with deliverability notes and a worked cost example at canonical rates (10DLC $0.0135/msg + carrier, toll-free $0.016/msg + carrier). Author: Ali Gasimzade. May 1, 2026.
- https://otterblocx.com/blog/send-sms-mms-email-from-one-api-quickstart — Send your first SMS, MMS, and email from one API in 5 minutes. Copy-pasteable curl + Node snippets to send your first SMS, MMS, and email through the Blocx REST API in five minutes — no SDK, no setup ceremony. Author: Ali Gasimzade. April 30, 2026.
- https://otterblocx.com/blog/sms-email-2fa-without-twilio-blocx-verify — SMS + email 2FA without Twilio: a Blocx Verify walkthrough. End-to-end Verify walkthrough with SMS primary, email fallback, code samples, rate-limit tips, and a 10k-verifications/month cost example. Author: Ali Gasimzade. April 24, 2026.
- https://otterblocx.com/blog/inside-the-blocx-router — Inside the Blocx router: one API across five message transports. Author: Ali Gasimzade (Senior Engineer). Apr 17, 2026.
- https://otterblocx.com/blog/cost-per-delivered-message-2026 — Cost per delivered message: a teardown of SMS, RCS, Email, MMS, and Telegram in 2026. Author: Ali Gasimzade (Senior Engineer). Apr 14, 2026.
- https://otterblocx.com/blog/2fa-flows-that-survive-carrier-outages — Building a 2FA flow that survives carrier outages. Author: Ali Gasimzade (Senior Engineer). Apr 10, 2026.

## Useful URLs
- https://otterblocx.com/
- https://otterblocx.com/voice
- https://otterblocx.com/sdk
- https://otterblocx.com/pricing
- https://otterblocx.com/privacy
- https://otterblocx.com/terms
- https://otterblocx.com/lp/sms
- https://otterblocx.com/lp/email
- https://otterblocx.com/lp/verify
- https://otterblocx.com/sitemap.xml
- https://otterblocx.com/robots.txt