How to Warm Up a New Domain for Cold Email Campaigns

Learn how to properly warm up a new domain in 2025 to avoid spam folders and maximize cold email deliverability.

Why Domain Warm-Up Is Critical in 2025

In cold email outreach, your domain is your identity — and if inbox providers don’t trust it, your emails won’t reach their destination.

When you send cold emails from a new domain without warming it up, you risk: ❌ Landing in spam ❌ Damaging your sender reputation ❌ Getting blacklisted or blocked

That’s why domain warm-up is non-negotiable in 2025. Warming helps you build credibility with ISPs like Gmail, Outlook, and Yahoo — one email at a time. Let’s walk through the step-by-step process for warming a new domain the right way.

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What Is Domain Warm-Up?

Domain warm-up is the gradual process of building a positive sender reputation by slowly increasing your sending volume and demonstrating consistent, non-spammy behavior.

Think of it like gaining trust. Start slow, stay consistent, and engage genuinely.

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Step-by-Step: How to Warm Up a New Domain

✅ Step 1: Set Up DNS Authentication Records

Before you send anything, ensure your domain is authenticated with:

• SPF – Verifies which servers are allowed to send on your behalf

• DKIM – Ensures your email wasn’t tampered with in transit

• DMARC – Protects your domain from spoofing and sets handling rules

SenderWiz guides you through domain authentication and checks for proper alignment across records. You can also review SPF, DKIM, and DMARC setup in the documentation.

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✅ Step 2: Set Up Your Sending Infrastructure

You can warm your domain using:

• A reputable ESP (email service provider)

• Your own SMTP server (via Postfix, PowerMTA, etc.)

• Or a platform like SenderWiz, which allows custom SMTP creation via SenderAI

Use a custom domain email address (e.g., [e-mail]), not a Gmail/Yahoo address.

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✅ Step 3: Create a Realistic Sending Schedule

Start small and build over 2–4 weeks. A basic warm-up schedule might look like:

Day	Emails/Day
1	20
3	50
5	100
7	200
10	500
14+	1,000+

Important: Only increase volume if bounce and spam rates are low.

SenderWiz’s automated warm-up feature gradually ramps up volume and manages sending windows per timezone.

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✅ Step 4: Send to High-Engagement Recipients First

During warm-up, send to:

• Internal team members

• Friends or colleagues

• Verified and engaged contacts

Ask them to:

• Open the emails

• Mark them as “Not Spam” (if needed)

• Reply to the message (this signals real interaction)

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✅ Step 5: Monitor Deliverability Metrics

Track:

• Open rates (should be high: 40–70%)

• Bounce rates (should be < 2%)

• Spam complaints (should be 0%)

• Domain/IP reputation via Google Postmaster Tools

If issues appear, pause sending and fix the cause before continuing.

SenderWiz includes real-time monitoring, bounce management, and reply tracking to help you stay in the safe zone.

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✅ Step 6: Avoid These Mistakes During Warm-Up

🚫 Don’t buy or scrape email lists 🚫 Don’t use spammy subject lines 🚫 Don’t use link shorteners (e.g., bit.ly) 🚫 Don’t send image-only emails 🚫 Don’t send more than your current volume allows

Build reputation slowly — or risk throttling, blacklisting, or permanent spam placement.

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Bonus: Use Smart Rotation During Warm-Up

Even while warming, rotate:

• From names (e.g., Sarah from GrowthCo, S. Martin)

• Subject lines

• Email content

• SMTPs and IPs (if using multiple)

SenderWiz’s Rotation Engine automatically rotates email elements during warm-up to avoid fingerprinting.

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What Happens After Warm-Up?

Once your warm-up period is complete and your inbox placement is solid:

• You can begin cold outreach at scale

• Gradually test higher volumes

• Continue rotating senders and content

• Maintain hygiene and monitor reputation constantly

Think of domain warming not as a one-time task — but as an ongoing reputation strategy.

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Real-World Example: Startup Warm-Up Success

Scenario: A SaaS startup wanted to send cold emails to 30,000 prospects.

Process:

• Warmed up domain over 3 weeks

• Sent to internal and verified contacts first

• Used SenderWiz to automate SMTP setup, rotation, and scaling

• Maintained bounce rate <1%, reply rate >10%

Result: Achieved 90%+ inbox delivery with zero spam folder placement by week 4.

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Final Thoughts: Warm-Up or Miss Out

Cold email works — but only if it’s seen. And it’ll only be seen if your domain is trusted.

In 2025, warming up a new domain isn’t optional — it’s a must-have for inbox success, reputation protection, and campaign performance.

🔍 Ask yourself: Would you trust an unknown sender blasting thousands of emails on day one?

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Want to warm up your domain the right way — with no technical hassle? SenderWiz automates domain/IP warm-up, rotation, reply tracking, and scheduling, so you stay focused on growth — not spam filters.

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