Domain Warm-Up

What is Domain Warmup?

Domain warmup is the process of gradually increasing email sending volume from a new domain to establish a positive reputation with mailbox providers. Think of it as earning trust over time—email providers need to see consistent, positive sending behavior before they'll deliver your emails to the inbox.

The Warmup Philosophy:

Email providers trust domains that have a history of:

• Consistent sending patterns
• Low bounce rates
• High engagement
• No spam complaints
• Proper authentication

New domains have zero reputation. Warmup builds that reputation systematically.

Why Domain Warmup Matters

Skipping warmup is the #1 reason new cold email campaigns fail. Without proper warmup, even perfect emails will go to spam.

What Happens Without Warmup:

• Immediate spam filtering for high-volume sends
• Domain reputation damaged before it's established
• Wasted effort on emails nobody sees
• Potential domain blacklisting
• Having to abandon the domain entirely

The 21-Day Standard: Industry consensus recommends 14-21 days minimum for proper warmup. This isn't arbitrary—it's how long it takes for positive signals to accumulate across major mailbox providers.

Benchmarks

Recommended Warmup Schedule:

Days	Daily Emails	Cumulative Sent
1-3	5-10	15-30
4-7	10-15	55-105
8-14	15-25	160-280
15-21	25-50	435-730
22+	Gradual increase	Based on engagement

Key Metrics During Warmup:

• Bounce rate: Must stay below 2%
• Spam complaints: Must stay below 0.1%
• Engagement: Monitor opens and replies
• Placement: Test inbox placement weekly

Best Practices

1. Use Warmup Tools: Services like SmartLead, Instantly, Lemwarm automate the process
2. Start Small: 5-10 emails per day maximum for new domains
3. Increase Gradually: Never more than 20-30% increase day-over-day
4. Send to Engaged Contacts First: Known good addresses build reputation faster
5. Monitor Daily: Check bounce rates and spam complaints every day
6. Maintain Consistency: Send every day, not sporadically
7. Use Multiple Inboxes: Have backup inboxes ready for each domain
8. Test Placement: Verify emails are reaching inbox, not spam

Common Mistakes

• Starting with high volume (instant reputation damage)
• Increasing volume too quickly (triggers spam filters)
• Not monitoring bounce rates during warmup
• Sending to cold lists before warmup completes
• Skipping warmup entirely (domain will be ruined)
• Not having backup domains/inboxes available
• Warmup with purchased lists (guaranteed spam folder)
• Assuming one domain handles all volume (need multiple)

Key Takeaways

• Domain warmup builds reputation gradually over 14-21 days
• Start with 5-10 emails/day and increase slowly
• Skipping warmup permanently damages new domains
• Keep bounce rates below 2% and spam complaints below 0.1% during warmup
• Use warmup tools to automate peer-to-peer email exchanges
• Monitor placement daily—emails should go to inbox, not spam
• Have multiple domains warming simultaneously for scale
• Proper warmup is non-negotiable for cold email success

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Sources:

• 21 Cold Email Deliverability Best Practices for 2024 - Clay
• Email Domain Warm-up Strategies 2024 - LinkedIn