Email Glossary

Email Warmup

Email warmup is the process of gradually increasing the volume of emails sent from a new IP address or domain to establish a positive sender reputation with email providers. It's essential for achieving good deliverability.

Why Warmup Is Necessary

ISPs are suspicious of new senders. A brand new IP or domain sending thousands of emails immediately looks like a spammer.

During warmup, you prove you're a legitimate sender by:

  • ●Sending small volumes initially
  • ●Maintaining high engagement rates
  • ●Keeping complaints low
  • ●Gradually increasing volume

This builds trust with ISPs, who then allow more of your emails through to the inbox.

Warmup Timeline

A typical warmup schedule for a new domain:

Week 1: 50-100 emails/day Week 2: 200-500 emails/day Week 3: 500-1,000 emails/day Week 4: 1,000-2,500 emails/day Week 5: 2,500-5,000 emails/day Week 6: 5,000-10,000 emails/day Week 7-8: Continue doubling until target volume

The exact timeline depends on your engagement rates. High engagement (opens, clicks) lets you move faster. Poor engagement means slowing down.

Warmup Best Practices

  • ●Start with your best contacts - Most engaged, most likely to open
  • ●Send real emails - Fake warmup emails can backfire
  • ●Monitor metrics daily - Watch bounce rates, complaints, and placement
  • ●Slow down if needed - If metrics dip, reduce volume
  • ●Spread sends throughout the day - Don't blast all at once
  • ●Maintain consistency - Don't stop and restart
  • ●Warm up each ISP - Send to Gmail, Outlook, Yahoo proportionally

Signs Warmup Is Working

Good signs:

  • ●Open rates above 20%
  • ●Inbox placement improving
  • ●No blocklist appearances
  • ●Steady increase in allowed volume

Warning signs:

  • ●Open rates dropping
  • ●Increasing spam folder placement
  • ●Bounce rates above 2%
  • ●Spam complaints appearing

If you see warning signs, pause or reduce volume and investigate before continuing.

Related Terms

Email Deliverability

The ability of your emails to reach recipients' inboxes instead of spam.

Sender Reputation

A score ISPs assign to your sending IP and domain based on email behavior.

IP Reputation

The trustworthiness score assigned to an IP address based on its email sending history.

Frequently Asked Questions

Do I need to warm up if I'm using a shared IP?
Not typically, shared IPs are already warmed by other users' traffic. However, you still need to warm up your domain reputation. Start with lower volumes and your most engaged contacts.
How long does warmup take?
A full warmup typically takes 4-8 weeks depending on your target volume and engagement rates. Rushing it risks damaging your reputation. Some ISPs (especially Microsoft) take longer to trust new senders.
Can I automate warmup?
Yes. Transmit offers automated warmup that gradually increases your sending volume while monitoring engagement. Manual warmup requires careful daily monitoring and adjustment, which automated systems handle for you.
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Need help with email deliverability?

Transmit handles authentication, warmup, and reputation isolation automatically.