zend.shzend.sh
Our mission
Infrastructure, not another dashboard. The API is the product. The CLI is the interface. The MCP server is how AI agents run the system.
Why we built it
Every cold email tool forces you into their sending infrastructure. We don't. You bring your own Google Workspace, Microsoft 365, or custom SMTP/IMAP mailboxes. zend.sh orchestrates them.
The BYOK model changes the unit economics completely. No sending infrastructure capex. Gross margins above 90%. No conflict with transactional email provider terms of service that prohibit cold outreach. And full portability — your mailboxes, your domains, your reputation.
The free P2P warmup network follows the same philosophy. Users warm each other's accounts via standard IMAP/SMTP against real inboxes. No managed pool, no artificial engagement, no spam traps. The network scales with the user base — every new account makes everyone's warmup better.
The result: email infrastructure that is genuinely cheaper to run, impossible to be cut off from, and designed to survive at scale.
Not a dashboard with an API bolted on. The API is the primary interface — 80+ REST endpoints that let you orchestrate every aspect of programmatic cold email.
Ten command groups with narrative output, --json for scripting, and --yes for automation pipelines. Full terminal access to every operation.
58 tools across 15 domain modules. AI agents can manage campaigns, scale experiments, and monitor deliverability conversationally via the MCP server.
Connect your own Google Workspace, Microsoft 365, or custom SMTP/IMAP mailboxes. zend.sh orchestrates them and never sends from its own infrastructure.
Where we fit
"Resend for cold email" — API-first infrastructure vs the dashboard-first incumbents (Instantly, Smartlead, Lemlist). We're the execution layer, not the orchestration layer.
Prospect enrichment and data waterfall — populates the lead database before sequences begin.
LinkedIn automation layer — runs the top-of-funnel touchpoints before email.
The Antigravity orchestrator that sequences cross-channel outbound — decides when email fires.
The email execution layer. When the orchestrator says send, zend.sh handles rotation, warmup, scheduling, and delivery.
API-first vs dashboard-first. Instantly, Smartlead, and Lemlist are dashboard products with APIs bolted on. zend.sh is an API that happens to have a read-only status view. The primary interfaces are REST, CLI, and MCP. Your AI agent can run a full campaign lifecycle without a human opening a browser.
Where we are
We're early. The numbers below are real — the actual state of the platform today, not projections or vanity metrics.
Warmup network accounts
Active sending domains
Current stage
zend.sh is a private beta. We don't publish funding numbers, team size, or named customer logos — because we don't have any of those yet that we can stand behind publicly. What we do have is real infrastructure, real code, and real network numbers. We ship in the open. See the changelog for what ships every week.
Join the private beta. Connect your first mailbox in under two minutes.