Deliverability

Do you need email warmup? (yes — here's when and how)

Any new domain or mailbox sending cold email needs 2–3 weeks of warmup before real campaigns, or it lands in spam. Established, well-reputed senders can skip it. Here's the rule.

18 Jun 2026 6 min readBy Autocloz Editorial, Deliverability team
Do you need email warmup? (yes — here's when and how)

Short answer: yes — if you're sending cold email from a new domain or mailbox, warm it up for 2–3 weeks before real campaigns, or mailbox providers read your sudden volume as spam. An established mailbox with a strong reputation and steady volume can skip it. A fresh one can't.

When you need warmup

  • New domain or subdomain → always.
  • New mailbox on an existing domain → yes, lighter.
  • Big jump in volume → ramp, don't spike.
  • Established, low-complaint mailbox at steady volume → skip.

How warmup works

Automated warmup sends and replies across a network of inboxes, building positive engagement signals — opens, replies, "not spam" marks — so providers learn your domain is trusted. Volume climbs slowly, from a few sends a day up to your target over roughly 3 weeks.

Built in, automatic

Autocloz warms every connected mailbox automatically and ramps volume safely, alongside DMARC, DKIM and SPF checks and bounce auto-pause.

> Start free — connect a mailbox and warmup starts automatically.

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Every tactic in this article is implemented behind the Autocloz dashboard.