Cold email infrastructure API
Cold outbound, programmatically.
Provision inboxes, launch 100 campaigns, and track every reply — from your terminal, API, SDKs, or an MCP agent.
…or one API call
curl -X POST https://app.zend.sh/api/v1/campaigns \
-H "Authorization: Bearer zk_live_..." \
-H "Content-Type: application/json" \
-d '{"name":"Q1 Outreach","stop_on_reply":true}'How it works
Cold outbound, end to end.
From first inbox to last reply — provision, launch, deliver, and analyze without stitching together six tools.
Scale
Launch 100 campaigns in seconds.
One command fans out across inboxes — sequences, rotation, and ramp, handled.
$ zend scale --experiment "Q1 Outreach" --daily-target 500 --leads leads.csv --ramp-days 14 ✓ Experiment created ✓ Ramping to 500/day over 14 days → Fanning out across inboxes…
Provision
Bring your own inboxes — or we provision them on Azure.
You own the domain; we wire SPF, DKIM, and DMARC and stand up mailboxes. Available via API and guided onboarding.
Bring your own inboxes
Connect existing mailboxes and start sending immediately. Zero infrastructure changes needed on your side.
- Google Workspace
- Microsoft 365
- Any SMTP / IMAP provider
- Full mailbox rotation + health scoring
- Warmup included — free forever
Or provision on Azure
Guided / API · not a one-step wizardGuided onboarding stands up the Azure ACS stack, Cloudflare DNS, and mailboxes. You receive API credentials and remain in control.
- Azure ACS stack provisioned via API
- Cloudflare DNS — SPF / DKIM / DMARC auto-pushed
- Mailboxes + sender identities created
- Available via REST API and guided onboarding
How it works
01You own the domain
Add your domain and DNS credentials once.
02We wire DNS + identities
SPF, DKIM, DMARC, and ACS sender identities pushed automatically.
03Mailboxes ready to send
Accounts enrolled in warmup, rotation, and health monitoring.
Analyze
See every send, reply, and risk signal.
Team / campaign by-step + by-day, account-health scores, AI Guardian assessments, and real-time webhooks.
Campaign activity — last 14 days
Illustrative dataBy-step + by-day breakdowns
Campaign and sequence analytics sliced by step, day, and account.
Per-account health scores
Bounce rate, complaint rate, and rotation weight tracked per mailbox.
AI Guardian assessments
Automated risk assessment and next-action recommendations per account.
Real-time webhooks
Bounce, reply, open, and complaint events streamed to your endpoint.
Built for your workflow
One platform, three ways in.
Developers automate it, agencies scale it, sales teams just send.
By the numbers
Real infrastructure, real numbers.
No vanity metrics — these are the actual capabilities of the platform today.
Compare
Built different from dashboard tools.
Infrastructure, not a seat-based app.
| Capability | zend.sh | Typical sending tools |
|---|---|---|
| Inbox provisioning | BYO or Azure (guided) | Manual / none |
| API · CLI · MCP | REST (80+), CLI, 58 MCP tools | Dashboard-first |
| Free warmup | Free forever | Paid add-on |
| Pricing model | Per email | Per seat / per inbox |
| Tracking pixels | Off by default | On by default |
Frequently Asked Questions
Everything you need to know about cold email infrastructure with zend.sh.