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Overview

SendyKit self-hosted uses EDD Software Licensing-powered license verification. Your license key determines your edition (Standard or Pro) and unlocks the corresponding features. Human checkout, licensing, and subscription mechanics run through Easy Digital Downloads on sendykit.dev.

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How It Works

1

Purchase

Buy a license at sendykit.dev/pricing. You receive a license key: sk_lic_xxxxxxxxxxxxx
2

Install

curl -sSL https://install.sendykit.dev | bash
The installer prompts for your license key and validates it.
3

Validate

On first launch, the Go binary contacts the SendyKit licensing API to verify your key and download your entitlements (edition, features, metered service access).
4

Run

The binary caches your entitlements locally. Weekly heartbeat checks for updates. 30-day offline grace if the licensing server is unreachable.

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Safety Guarantees

We take these seriously. SendyKit will never brick your installation.
GuaranteeWhat It Means
Fail-openIf the licensing server is down, your binary keeps running with cached entitlements. It never stops working.
30-day offline graceAfter 30 days without a heartbeat: you see a warning banner. Not a shutdown. All features keep working.
No data exfiltrationZero customer data leaves your server. No emails, subscriber lists, campaign content, API keys, or PII are ever transmitted.
Transparent loggingEvery phone-home request is logged to sendykit.log. You can audit exactly what’s sent.
Auditable payloadThe heartbeat sends only: license_key, version, os, arch, subscriber_tier (a range, not exact count), uptime_days. Nothing else.
Fully disable-ableSet SENDYKIT_OFFLINE=true to disable all phone-home. License cached indefinitely. No nag screens.
No kill switchThe binary never self-disables. Even with an expired or revoked license: warning banner only. All features keep working.
Open heartbeat specThe heartbeat format is documented here so you can firewall-verify what’s transmitted.

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Heartbeat Payload

{
  "license_key": "sk_lic_xxxxx",
  "version": "1.2.0",
  "os": "linux",
  "arch": "amd64",
  "subscriber_tier": "1k-5k",
  "feature_flags_hash": "a1b2c3d4",
  "uptime_days": 42
}
The subscriber_tier is a range bucket (e.g., “1k-5k”), not an exact count. We never know your actual subscriber count.

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Editions

FeatureStandardPro
REST API (125 endpoints)✅✅
CLI (240+ commands)✅✅
Analytics Intelligence✅✅
Health Doctor (68 checks)✅✅
SMTP Overlay✅✅
Audit Trail✅✅
Admin UI (7 pages)✅✅
Visual Editor (GrapeJS)✅✅
AI Authoring—✅
Sequences & Funnels—✅
Automations—✅
Priority Support—✅
White Label—✅

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Metered Add-Ons

Self-hosted customers can optionally purchase metered services that run through SendyKit’s infrastructure:
ServiceWhatPricing
SMTP Pool OverflowWhen your SES quota is exhausted, SendyKit routes overflow emails through our managed SMTP providers$3-5/1000 emails
AI Content CreditsAI requests proxied through SendyKit’s API — no need for your own OpenAI/Anthropic key$0.002/generation
Deliverability ShieldContinuous DNS/reputation monitoring from SendyKit’s servers$49/year
Priority SupportFaster response times, dedicated support queue$99/year
Usage is tracked natively by SendyKit. Human purchases and add-on checkout run through EDD on sendykit.dev, using the card attached to your customer account when applicable.

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Offline Mode

For air-gapped or restricted environments:
.env
SENDYKIT_OFFLINE=true
SENDYKIT_LICENSE_KEY=sk_lic_xxxxxxxxxxxxx
In offline mode:
  • No network requests to SendyKit servers
  • License validated from local cache only
  • Metered add-ons (SMTP pool, AI credits) unavailable
  • All installed features work normally
  • No update notifications