The Email API, Rebuilt

Email delivery that's10x cheaperand actually simple

Every legacy provider overcharges you because they run on expensive, inefficient infrastructure. InboxFlow is built on Rust + Cloudflare — 60-80% cost savings, one-line API, zero overage.

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60-80%

Cost savings vs legacy providers

50K+

Concurrent connections per node

<1ms

API response time at edge

99.99%+

Uptime SLA on Enterprise

The Problem

Why does email deliverycost so much?

Legacy providers run on traditional cloud infrastructure with garbage-collected languages. They need 5x more servers per connection. Those costs get passed to you.

Infrastructure cost$19.95/100K emails$2.50-$4/100K emails
Overage billingAutomatic surprise billsNever. You choose when to upgrade.
Connection density~10K connections/node50K+ connections/node
Runtime overheadGC pauses, higher memoryZero-cost abstractions, Rust
Pricing transparency"Contact sales" for enterprisePrices on website. Always.

Cost per 100K emails

SendGrid$19.95
Mailgun$18.50
AWS SES$10.00
InboxFlow$2.50 – $4.00
Up to 87% cheaper
Our IP

Built different from the ground up

We didn't fork SendGrid. We rebuilt email infrastructure from scratch with modern tools that give us a real advantage — and pass the savings to you.

Rust-Powered Core

Every connection handler, parser, and router is written in Rust. No garbage collector, no runtime overhead. Just raw performance and memory safety.

  • 50K+ connections per node
  • Zero-cost abstractions
  • Tokio async I/O runtime

Cloudflare Edge

We run on Cloudflare's global network. Tracking pixels, link redirects, and webhooks execute at the edge — within milliseconds of your users anywhere in the world.

  • Workers for edge compute
  • R2 storage, zero egress fees
  • Durable Objects for state

No Overage. Ever.

Legacy providers auto-charge you when you exceed your plan. We don't. You choose when to upgrade. No surprise bills, no "overage forgiveness" games.

  • Notify before you hit limits
  • Instant upgrade, no prorating
  • All features at every tier
    • How We Deliver

    Your email's journey, optimized

    Every email passes through our pipeline in under 100ms. Here's what happens when you hit "send."

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    SMTP Ingress

    50K+ concurrent connections per node. Built with Rust + Tokio for maximum throughput and memory safety.

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    API Gateway

    Type-safe HTTP API built with Axum. Automatic rate limiting, validation, and idempotency.

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    Delivery Engine

    Intelligent routing with automatic IP warming, bounce handling, and suppression management.

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    Edge Tracking

    Open & click tracking at the edge via Cloudflare Workers. Zero latency impact on your emails.

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    Analytics Pipeline

    Real-time processing of delivery events. Webhooks with automatic retries and idempotency.

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    Control Plane

    Configuration, template rendering, domain verification via Durable Objects.

    Everything Included

    All the tools to ship email

    Every feature at every tier. No gating, no enterprise upsells, no "premium" add-ons.

    One-Line API

    Send email with a single HTTP request or SDK call. No complex setup, no boilerplate.

    SMTP Relay

    Full SMTP relay support for existing infrastructure. Works with any SMTP library.

    Open Tracking

    Transparent tracking pixel injection. See who opened and when, in real-time.

    Click Tracking

    Automatic link rewriting. Track every click without slowing down your users.

    Email Templates

    Store and manage templates with dynamic variables. Preview before sending.

    Webhook Delivery

    Real-time event notifications. Automatic retries with exponential backoff.

    Domain Management

    DKIM, SPF, and DMARC setup wizard. Automatic DNS verification.

    Team Management

    RBAC with granular permissions. Audit logs for every action.

    Suppression Management

    Automatic bounce and complaint handling. Global and per-domain suppression lists.

    Rate Limiting

    Per-account and per-IP rate limiting. No noisy neighbor problems.

    Dedicated IPs

    Reserved IPs for high-volume senders. Automatic warmup scheduling.

    SSO/SAML

    Enterprise-grade authentication. Okta, Azure AD, Google Workspace, and any SAML 2.0 provider.

    Plus: Dedicated IPs, SSO/SAML, sub-accounts, custom data residency — all available without "contact sales."
    Trust & Security

    Enterprise-grade security.
    Built in from day one.

    We handle your email data the same way we'd want ours handled. Encrypted everywhere, SOC 2 audited, and configurable down to the storage region.

    View security docs

    Encryption at Rest

    All data encrypted with AES-256. Your email content never stored unencrypted.

    Encryption in Transit

    TLS 1.3 for all connections. STARTTLS mandatory for SMTP.

    SOC 2 Compliance

    SOC 2 Type II certified. Annual audits by independent firms.

    Audit Logs

    Every action logged. Configurable retention from 90 days to 7 years.

    API Authentication

    API key-based auth with automatic rotation. Fine-grained permission scopes.

    Data Residency

    Choose data storage regions: US, EU, APAC, or custom for enterprise.

    Why InboxFlow

    Why teams are switching

    Developers choose InboxFlow because it's simpler, cheaper, and more transparent.

    60-80% cost savings

    Our Rust + Cloudflare infrastructure is fundamentally more efficient. We pass every penny of savings to you.

    One-line integration

    One HTTP request. One SDK call. No complex setup, no weeks of migration. Grab an API key and start sending.

    No surprise bills

    No overage billing. No auto-charges. No "you went over by 2%, here's a $500 bill." You control when you upgrade.

    Get Started Free

    Start sending in under 2 minutes

    No credit card. No onboarding call. No "talk to sales." Just one API key and you're shipping.

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