Complete Cold Email Infrastructure Setup Guide 2025

By Muhammad Wani | January 6, 2025 | 12 min read

Your cold email infrastructure is the foundation of everything. Get it wrong and your emails go to spam. Get it right and you can scale to millions of emails with 95%+ inbox placement.

I've set up cold email infrastructure for 40+ clients and sent over 5 million emails. This is the exact process I use every time.

This guide covers everything: domains, DNS records, email accounts, warmup, monitoring, and troubleshooting. By the end, you'll have bulletproof infrastructure that supports sustainable, scalable cold email campaigns.

Why Cold Email Infrastructure Matters

Most people think cold email is about copy and targeting. Those matter, but infrastructure comes first.

Here's what happens with bad infrastructure:

Good infrastructure? Your emails reach the inbox. It's that simple.

Real Example: A client came to me with 23% inbox placement. Same copy, same targeting, just fixed the infrastructure. Inbox placement went to 94% within two weeks. Their reply rates went from 1.8% to 11.2%.

The Complete Cold Email Infrastructure Stack

Here's what you need for proper cold email infrastructure setup:

  1. Sending Domains: Separate domains from your main business domain
  2. DNS Authentication: SPF, DKIM, and DMARC records properly configured
  3. Email Accounts: Multiple accounts per domain, properly set up
  4. Email Warmup: Gradual sending volume increase with engagement simulation
  5. Sending Infrastructure: Cold email platform with proper rotation
  6. Monitoring Tools: Track deliverability, reputation, and blacklists

Let's go through each component step by step.

Step 1: Choosing and Buying Sending Domains

Why You Need Separate Domains

Never send cold emails from your main business domain. Here's why:

Use separate sending domains that are similar to your main domain but clearly different.

Domain Selection Strategy

If your main domain is mybusiness.com, your sending domains could be:

Warning: Don't use domains that are too similar (mybusiness.net, mybusinesss.com). These look like phishing attempts and hurt deliverability. Make them obviously intentional variations.

How Many Domains Do You Need?

The answer depends on your sending volume:

General rule: Each domain should send no more than 50 emails per day per email account during the first month.

Where to Buy Domains

Recommended domain registrars for cold email infrastructure:

Avoid: Free domain services or shady registrars. You want reputable registrars for deliverability.

Domain Age Considerations

New domains have lower trust scores. Here's the timeline:

You can buy aged domains (1+ years old) for faster warmup, but they're expensive and may have history issues.

Step 2: DNS Authentication Setup (SPF, DKIM, DMARC)

This is where most people mess up cold email infrastructure setup. DNS authentication tells email providers "this email is legitimate and authorized."

What Are SPF, DKIM, and DMARC?

SPF (Sender Policy Framework): Lists which servers can send email from your domain.

DKIM (DomainKeys Identified Mail): Adds a digital signature to your emails proving they came from your domain.

DMARC (Domain-based Message Authentication, Reporting & Conformance): Tells email providers what to do if SPF or DKIM fails.

All three are required for good deliverability in 2025. Missing even one significantly hurts inbox placement.

Setting Up SPF Records

SPF record structure for cold email:

v=spf1 include:_spf.google.com include:spf.instantly.ai ~all

Breaking this down:

Add SPF as a TXT record in your DNS settings with these values:

Setting Up DKIM Records

DKIM setup depends on your email platform. For Google Workspace:

  1. Go to Google Admin Console
  2. Navigate to Apps > Google Workspace > Gmail
  3. Click "Authenticate email"
  4. Generate DKIM key
  5. Copy the TXT record provided
  6. Add to your DNS as TXT record

For cold email platforms (Instantly, Smartlead, etc.), they'll provide DKIM records in their domain setup wizard.

Your DKIM record will look something like:

google._domainkey.yourdomain.com TXT "v=DKIM1; k=rsa; p=MIGfMA0GCSqGSIb3..."

Setting Up DMARC Records

DMARC is simpler. Add this as a TXT record:

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

Setting details:

Policy options for DMARC:

Pro Tip: Start with p=none for the first 30 days while you monitor deliverability. Once everything is stable, upgrade to p=quarantine for better domain protection.

Verifying DNS Records

After adding DNS records, verify they're working:

  1. Use MXToolbox.com to check SPF, DKIM, and DMARC
  2. Enter your domain
  3. Look for green checkmarks on all three
  4. Wait 24-48 hours for full propagation if not showing immediately

Step 3: Setting Up Email Accounts

How Many Email Accounts Per Domain?

General rule: 3-5 email accounts per domain.

Why not more?

Email Account Naming Conventions

Use realistic names that match real business roles:

Avoid:

Email Provider Options

Google Workspace (Recommended):

Microsoft 365:

Private SMTP (Not Recommended for Beginners):

Important: Don't use free email accounts (Gmail, Outlook, Yahoo) for cold email. They'll shut you down immediately and potentially ban your accounts permanently.

Step 4: Email Warmup Process

Email warmup is gradually increasing sending volume while building positive engagement signals. Skip this and your emails go straight to spam.

Why Email Warmup Is Critical

New email accounts have zero reputation. Email providers don't trust them. You need to:

Manual vs Automated Warmup

Manual warmup: You manually send emails to friends/colleagues who reply. Time-consuming and doesn't scale.

Automated warmup: Tools like Instantly, Smartlead, or Mailreach send emails between warmup accounts and simulate real engagement. This is the standard approach.

Warmup Timeline and Volume

Here's the exact warmup schedule I use for every cold email infrastructure setup:

Week 1:

Week 2:

Week 3:

Week 4:

Month 2+:

Critical Rule: Never increase volume by more than 20% per week during warmup. Sudden jumps trigger spam filters.

Warmup Best Practices

  1. Keep warmup running forever: Don't stop after 30 days. Keep 10-20% of your volume as warmup permanently.
  2. Vary sending times: Don't send all emails at 9am. Spread throughout the day (8am-6pm).
  3. Monitor inbox placement: Check where emails are landing (inbox vs spam).
  4. Watch for warnings: If inbox placement drops below 80%, slow down immediately.

Step 5: Sending Patterns and Volume Management

Daily Sending Limits

Safe sending limits per account after warmup:

These are conservative numbers. You can push higher, but risk increases.

Sending Time Optimization

Spread your emails throughout the workday:

Account Rotation Strategy

Rotate between accounts to distribute sending:

Always leave 30% buffer for safety.

Step 6: Monitoring and Maintenance

Key Metrics to Track

  1. Inbox Placement Rate: % of emails landing in inbox (target: 90%+)
  2. Spam Rate: % of emails in spam folder (target: under 5%)
  3. Bounce Rate: % of emails that bounce (target: under 3%)
  4. Open Rate: % of emails opened (target: 30-50%)
  5. Reply Rate: % of emails getting replies (target: 5-15%)

Tools for Monitoring

Deliverability testing:

Blacklist monitoring:

Warning Signs to Watch For

If you see any of these, pause sending immediately:

Step 7: Troubleshooting Common Infrastructure Issues

Problem: Emails Going to Spam

Causes:

Solutions:

Problem: Domain Blacklisted

Causes:

Solutions:

Problem: Low Open Rates

Causes:

Solutions:

Cold Email Infrastructure Setup Checklist

Complete Setup Checklist:

Domain Setup:

DNS Configuration:

Email Accounts:

Warmup:

Platform Setup:

Monitoring:

Advanced Infrastructure Optimization

Custom Tracking Domains

Most cold email platforms add tracking links that can trigger spam filters. Using a custom tracking domain helps:

Dedicated IP Addresses

For very high volume (50,000+ emails/day):

Multiple Platform Strategy

For maximum reliability:

Common Mistakes to Avoid

  1. Rushing warmup: Most common mistake. 30 days minimum, no shortcuts.
  2. Using main domain: One bad campaign can ruin your business domain forever.
  3. Ignoring DNS: Missing SPF/DKIM/DMARC = automatic spam folder.
  4. Too many accounts per domain: More than 5 looks suspicious.
  5. Not monitoring: Check inbox placement weekly at minimum.
  6. Sudden volume increases: Scale gradually (20% increase per week max).
  7. Stopping warmup: Keep it running forever in background.
  8. Buying email lists: High bounce rates destroy sender reputation.

Infrastructure Costs Breakdown

Here's what you'll spend for basic cold email infrastructure setup:

Total: $85-200/month for infrastructure supporting 300-500 emails/day

This scales linearly. Double the capacity = roughly double the cost.

Final Thoughts

Cold email infrastructure setup isn't sexy, but it's the difference between 30% inbox placement and 95% inbox placement.

I see businesses spend thousands on copy, targeting, and tools while ignoring infrastructure. Then they wonder why nothing works.

Set up your infrastructure correctly once. Then you can focus on what actually generates results: copy, targeting, and follow-up strategy.

The time investment is front-loaded. Two days of proper setup saves months of troubleshooting and burned domains.

Do it right the first time.

Need Help Setting Up Your Cold Email Infrastructure?

I've set up infrastructure for 40+ clients. Takes 2-3 days, includes DNS configuration, account setup, warmup strategy, and monitoring setup. Everything you need to scale safely.

Book Infrastructure Setup Call

About the Author: Muhammad Wani has set up cold email infrastructure for 40+ clients and sent over 5 million cold emails with 95%+ inbox placement. He helps businesses build scalable outreach systems at AI Agenix.

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