Email Warm-up Guide: How to Build Sender Reputation

Launching a new email domain or IP address without warming up is like running a marathon without training—you'll crash. Email warm-up builds your sender reputation gradually, ensuring your emails reach inboxes instead of spam folders.

What is Email Warm-Up?

Email warm-up is the process of gradually increasing your sending volume to establish a positive sender reputation with ISPs (Gmail, Outlook, Yahoo, etc.).

When you need warm-up:

• New email domain
• New dedicated IP address
• Long period of inactivity (6+ months)
• Migrating to a new email service provider
• Starting cold email outreach

Why Warm-Up Matters

ISPs are suspicious of new senders. A brand new domain suddenly sending thousands of emails looks like a spammer. Without warm-up:

• Your emails go straight to spam
• ISPs throttle or block your sends
• Your sender reputation starts in the negative
• You might get blacklisted
• Recovery takes months

The Email Warm-Up Schedule

Warm-up typically takes 4-8 weeks. Here's a proven schedule:

Week 1: Start Small

• Day 1: Send 50 emails
• Day 2: Send 75 emails
• Day 3: Send 100 emails
• Day 4: Send 150 emails
• Day 5: Send 200 emails

Target: Your most engaged subscribers. People who definitely want to hear from you.

Week 2: Double Weekly

• Send 300-500 emails per day
• Continue targeting engaged subscribers
• Monitor bounce and spam rates closely

Week 3-4: Increase Gradually

• Week 3: 1,000-2,000 emails per day
• Week 4: 3,000-5,000 emails per day

Week 5-8: Reach Full Volume

• Week 5: 7,500 emails per day
• Week 6: 10,000 emails per day
• Week 7-8: Full intended volume

Warm-Up Best Practices

1. Start with Your Best Subscribers

Send to people who open every email. High engagement during warm-up builds positive reputation quickly.

2. Keep Engagement High

Send valuable, relevant content. You want opens, clicks, and ideally replies during warm-up.

3. Maintain Consistent Volume

Don't send 500 Monday, skip Tuesday, then send 1,000 Wednesday. Consistency matters.

4. Monitor Key Metrics

Watch these metrics daily during warm-up:

• Bounce rate: Should stay under 2%
• Spam complaint rate: Must stay under 0.1%
• Open rate: Should be high (25%+)
• Unsubscribe rate: Under 0.5%

If any metric spikes, pause and investigate before continuing.

5. Authenticate Everything

SPF, DKIM, and DMARC must be set up BEFORE you start warm-up. Non-negotiable.

6. Avoid Spam Triggers

During warm-up, be extra careful with content. Test every email before sending.

Automated Warm-Up Services

Several services automate warm-up by exchanging emails with other users in their network:

• Warmup Inbox
• Lemwarm (by Lemlist)
• Mailwarm (by Mailreach)
• GMass warm-up

Pros: Automated, consistent engagement signals

Cons: Costs $30-100/month, engagement is artificial

Red Flags to Avoid During Warm-Up

• Jumping volume too fast
• Sending to purchased or old lists
• Ignoring bounces
• Using spam trigger words
• Sending identical emails to everyone
• Skipping weekends (maintain 7-day schedule)
• Sending cold emails during warm-up

What to Do If Warm-Up Fails

If you see high bounces, spam complaints, or your emails suddenly go to spam:

• Pause sending immediately
• Identify the issue (list quality? content? authentication?)
• Fix the problem
• Clean your list thoroughly
• Resume at 50% of previous volume
• Increase more slowly