Domain Warmup Complete Guide 2026: 0 to 50 Emails/Day in 21 Days

Skip domain warmup = spam folder death.

I warmed up 200+ domains over 3 years. Here's the exact process that maintains 95% inbox placement.

Why Warmup Matters in 2026

Gmail and Outlook got stricter in 2025:

• New domains flagged immediately
• Sending volume monitored closely
• Spam complaints = instant blacklist
• Engagement rate now matters more than ever

Without warmup: Your emails land in spam within 3 days

With proper warmup: 95%+ inbox placement maintained

The Complete 21-Day Warmup Schedule

DNS Setup (BEFORE Warmup)

Your domain needs proper DNS records before starting warmup:

SPF Record

What it does: Authorizes your sending server

Example:

v=spf1 include:_spf.google.com ~all

DKIM Record

What it does: Authenticates your emails

How to set up: Google Workspace provides DKIM key automatically

DMARC Record

What it does: Tells ISPs how to handle failed authentication

Example:

v=DMARC1; p=none; rua=mailto:dmarc@yourdomain.com

Custom Tracking Domain

What it does: Tracks opens/clicks without hurting deliverability

Setup: Point track.yourdomain.com to sending platform

For complete DNS setup, see our infrastructure guide.

Tools for Warmup

Option 1: Warmbox ($19/mailbox)

Pros: Dedicated warmup tool, works well

Cons: Costs add up with many domains

Best for: 1-10 domains

Option 2: Instantly Warmup (included)

Pros: Free with Instantly subscription

Cons: Requires Instantly account

Best for: Already using Instantly

Option 3: Smartlead Warmup (included)

Pros: Included in Smartlead

Cons: Need Smartlead subscription

Best for: Smartlead users

Option 4: MailReach ($25/mailbox)

Pros: Best deliverability testing included

Cons: More expensive

Best for: Want detailed deliverability data

Monitoring Warmup Progress

Check these metrics daily:

1. Inbox Placement Rate

Should be 95%+ after Day 14

Tool: GlockApps or MailReach

2. Bounce Rate

Should be under 2%

If higher: Your list quality is bad

3. Spam Complaints

Should be 0%

If any: Stop sending immediately, investigate

4. Engagement Rate

Warmup emails: 80%+ engagement

Real emails: 10-20% engagement

Common Warmup Mistakes

Mistake 1: Rushing the Process

Problem: Going 0 to 50 emails in 7 days

Result: Spam folder by day 10

Solution: Follow 21-day schedule

Mistake 2: No DNS Setup

Problem: Starting warmup without SPF/DKIM/DMARC

Result: Emails rejected immediately

Solution: Set up DNS first

Mistake 3: Stopping Warmup Too Early

Problem: Stopping warmup after reaching 50/day

Result: Deliverability degrades over time

Solution: Keep 20-30 warmup emails/day forever

Mistake 4: Sending Only Cold Emails

Problem: 100% of volume is cold (low engagement)

Result: ISPs flag as spam

Solution: Maintain 40-50% warmup emails

Scaling to Multiple Domains

To send 500 emails/day, you need 10 domains:

• Each domain sends 50/day
• 10 domains × 50 = 500 emails/day total

Warmup strategy for 10 domains:

1. Buy all 10 domains
2. Set up DNS for all 10
3. Start warmup on all 10 simultaneously
4. Follow same 21-day schedule
5. After Day 21: Send 50/day per domain

For complete scaling guide, see how to scale to 15,000 emails/day.

Troubleshooting

Problem: Emails Going to Spam on Day 12

Likely cause: Scaled too fast

Fix: Drop back to Day 8 volume, slower ramp

Problem: High Bounce Rate (5%+)

Likely cause: Bad email list

Fix: Verify emails before sending with Hunter or ZeroBounce

Problem: Domain Blacklisted

Likely cause: Spam complaints or high bounces

Fix: Stop sending, request removal from blacklists

Warmup Checklist

Before starting:

• ✅ Domain purchased (aged 7+ days)
• ✅ Google Workspace set up
• ✅ SPF record configured
• ✅ DKIM record configured
• ✅ DMARC record configured
• ✅ Custom tracking domain set up
• ✅ Warmup tool selected
• ✅ Monitoring tools ready

During warmup:

• ✅ Check inbox placement daily
• ✅ Monitor bounce rate
• ✅ Watch spam complaints
• ✅ Follow volume schedule
• ✅ Don't skip days

Cost Breakdown

For 1 domain warmup (21 days):

• Domain: $12/year
• Google Workspace: $6/month
• Warmup tool: $19/month (Warmbox)
• Monitoring: $79/month (GlockApps)

Total first month: $105

Ongoing: $25/month per domain

Final Recommendations

Follow this exact schedule:

1. Set up DNS properly (Day 0)
2. Start warmup at 5 emails/day (Day 1)
3. Increase slowly following schedule (Days 2-21)
4. Maintain 50% warmup emails forever
5. Monitor deliverability weekly

For complete cold email setup, check our infrastructure guide.

— Muhammad
AI Agenix