zend.shzend.sh
Protection layers
Deliverability is not a single dial — it is five independent systems working in parallel. Each layer catches failure modes the others miss. Together they keep your emails out of spam.
P2P Warmup (free)
28-day ramp with AI-generated content. Spam rescue, reply simulation, mark-as-important. Sender reputation grows on autopilot before you send a single cold email.
Health Monitoring (0–100 scores)
Per-account health scores based on bounce rate, complaint rate, SMTP error rate, and engagement. Auto-pause cold sending when health degrades; auto-increase warmup to recover.
Blacklist Monitoring (50+ blacklists)
Daily checks against Spamhaus SBL/XBL/PBL/DBL, Barracuda, SpamCop, SORBS, UCEPROTECT, SURBL, and more. Instant alerts with step-by-step delisting guidance.
DNS Health (SPF / DKIM / DMARC / MX / rDNS)
Automated verification of SPF, DKIM (multi-selector), DMARC, MX, and rDNS. Catches accidental changes that silently break authentication and tank inbox placement.
Inbox Placement Testing
Send test emails to seed mailboxes across Gmail, Outlook, and Yahoo. Verify via IMAP whether they landed in inbox, spam, or promotions. Know your actual placement rate.
Automatic protection
Six triggers — all checked in real time. When a threshold is crossed, zend.sh acts immediately: pausing cold sends, boosting warmup volume, firing webhook alerts, and logging the event. No dashboard refresh required.
Bounce rate > 2%
Auto-pause cold sending, increase warmup volume to recover reputation.
Complaint rate > 0.3%
Auto-pause cold sending, fire webhook alert to your endpoint.
3+ consecutive SMTP errors
Mark account as error state, stop all sends on that mailbox.
Domain blacklisted
Alert with step-by-step delisting guidance, pause cold sends.
SPF / DKIM / DMARC fails
Alert immediately and flag prominently in the dashboard.
Health score < 60
Boost warmup volume automatically, restrict cold sends until health recovers.
Two hard thresholds: bounce rate above 2% and complaint rate above 0.3%. Either crossing triggers an immediate pause on cold sends and a webhook event to your configured endpoint. A health score below 60 triggers a softer response — boosted warmup volume and restricted cold sends — without a full pause.
50+ lists checked daily, including Spamhaus (SBL, XBL, PBL, DBL), Barracuda, SpamCop, SORBS, UCEPROTECT L1/L2/L3, SURBL, and more. When a listing is detected, you get an alert with the specific list, the listed IP or domain, and step-by-step delisting instructions.
We send test emails to seed mailboxes across Gmail, Outlook, and Yahoo that we control. After delivery, we check via IMAP where the message landed: inbox, spam, or promotions tab. This tells you your real placement rate — not a score estimate, but actual folder outcomes.