zend.shzend.sh
How it works
Every inbox provider watches how people interact with your emails. Warmup simulates positive engagement at scale — automatically, across a real P2P network.
The ramp
We start slow and increase gradually — exactly how a real growing business looks to inbox providers. No sudden spikes that trigger spam filters. Day 1–3: 2/day. Days 4–7: 3/day. Days 8–14: 5–8/day. Days 15–21: 10–12/day. Days 22–28: 15/day. Day 29+: 5–10/day maintenance.
$ zend accounts warmup acct-1234
state: warming
ramp_day: 14
target_volume: 8
sends_today: 6
health_score: 94
estimated_ready: 2026-04-11Engagement
Every action happens through standard IMAP/SMTP — never unauthorized APIs. The same way a real person would interact. Six distinct engagement signals build lasting trust with Gmail and Outlook.
Spam rescue
When your email lands in spam, we move it to the inbox. Tells Gmail this sender is legitimate — the strongest positive signal.
Reply with delay (40% rate)
AI-generated unique replies, delayed 10 minutes to 8 hours. Never the same reply twice.
Mark as important (25% rate)
Emails get starred or flagged. Gmail interprets this as 'this sender matters to me.'
AI content — anti-detection
Every warmup email is unique. Generated by AI to look like real business communication — Gmail cannot fingerprint identical templates.
Randomized timing
Random send intervals (30s–15min), weekend volume reduction, daily jitter. Nothing predictable, nothing robotic.
Health monitoring
Blacklist checks against 50+ lists, DNS health verification, inbox placement testing. Auto-pause before damage.
Network effect
More inboxes in the warmup pool means more diverse engagement signals. Gmail detects closed loops between cold senders — our free tier brings in real business users who diversify the network for everyone.
Accounts in the network
Unique domains
Day ramp to full reputation
Yes — free forever, no credit card required. Every user who joins the warmup network strengthens it for everyone, so giving warmup away aligns our incentives with yours. There is no paid warmup tier.
When a warmup email lands in your spam folder, another inbox in the P2P network moves it to the inbox. This is the strongest positive signal you can send to Gmail: a real person decided your email was legitimate. It happens via standard IMAP — no unauthorized APIs.
Real engagement through real IMAP/SMTP. 40% of warmup emails get a genuine reply (AI-generated, unique per email). 25% get starred or flagged as important. Emails are rescued from spam by other inboxes. None of these actions use fake pixel tracking or unauthorized API calls — they look identical to real human behavior because they use the same protocols.