Cold Email Infrastructure

Technical setup including domains, authentication, warm-up, and monitoring.

What is Cold Email Infrastructure?

Cold email infrastructure is the technical foundation that enables your emails to reach inboxes instead of spam folders. It encompasses domains, email accounts, authentication protocols, warm-up processes, and monitoring systems.

Infrastructure Components:

Domains: Primary and secondary sending domains
Email Accounts: Inboxes across multiple domains
Authentication: SPF, DKIM, DMARC protocols
Warm-up: Gradual reputation building
Monitoring: Deliverability tracking and alerts

Without proper infrastructure, even perfectly written cold emails will never be seen.

Why Infrastructure Matters

The Deliverability Multiplier

Infrastructure determines if your emails arrive.

The Math:

Perfect copy + poor infrastructure = 60% inbox placement
Good copy + excellent infrastructure = 87%+ inbox placement

Infrastructure is the multiplier that determines whether your other investments (copy, lists, tools) pay off.

Long-Term Asset Protection

Good infrastructure protects your ability to email.

Infrastructure Value:

Protects primary domain reputation
Enables scalable outreach
Reduces risk of blacklisting
Provides predictable results

Competitive Advantage

Most teams neglect infrastructure.

Reality:

Average team: 60-70% inbox placement
Well-infrastructured team: 85%+ inbox placement
Difference: 2-3x more emails seen

Infrastructure Components

1. Domain Strategy

Separate domains for different purposes.

Domain Types:

Primary domain: company.com (business operations, customer emails)
Secondary domains: outreach.company.com, company.co (cold email only)

Why Secondary Domains:

Protects primary domain from spam complaints
Isolates cold email risks
Enables recovery if reputation damaged
Allows multiple sending identities

2. Email Account Setup

Multiple accounts per domain for volume.

Setup Guidelines:

2-3 inboxes per secondary domain
Maximum 25-50 emails per inbox daily
Spread volume across accounts
Never exceed 100 emails/day from single account

Example for 500 emails/day:

10 secondary domains
3 inboxes per domain = 30 inboxes total
~17 emails per inbox daily

3. Email Authentication

Required protocols for inbox placement.

SPF (Sender Policy Framework):
v=spf1 include:serviceprovider.com ~all

DKIM (DomainKeys Identified Mail):
Cryptographic signature verifying email authenticity.

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

Without all three: Major email providers flag your emails as suspicious.

4. Domain Warm-Up

Building reputation gradually.

Warm-Up Schedule:

Week 1: 5-10 emails daily per inbox
Week 2: 15-25 emails daily
Week 3: 25-40 emails daily
Week 4+: 40-50 emails daily

Duration: Minimum 21 days, ideally 30 days.

Why Warm-Up Matters:

New domains start with zero reputation
Sudden volume triggers spam filters
Gradual increase signals legitimate behavior
Engagement builds trust over time

5. Monitoring and Maintenance

Ongoing tracking essential for success.

Track Daily:

Bounce rates (keep under 2%)
Spam complaints (keep under 0.1%)
Inbox placement (test with seed accounts)
Open and reply rates
Domain health scores

Infrastructure Setup Process

Step 1: Domain Acquisition

Purchase or register secondary domains.

Best Practices:

Use brand-related names (outreach.company.com)
Purchase aged domains when possible (1+ years old)
Avoid domains with prior spam history
Whois privacy optional but not required

Step 2: DNS Configuration

Set up required DNS records.

Required Records:

MX records (email routing)
SPF record (sender authorization)
DKIM record (email signing)
DMARC record (authentication policy)
Reverse DNS (PTR records)

Step 3: Account Creation

Create email inboxes on each domain.

Account Setup:

Use Google Workspace or Microsoft 365
Create professional email addresses (name@domain.com)
Set up forwarding to central inbox
Enable IMAP for sending tools

Step 4: Authentication Verification

Confirm all protocols working.

Verification Steps:

Use SPF/DKIM/DMARC checkers
Send test emails to seed accounts
Verify headers show authentication passes
Check with tools like Mail-Tester.com

Step 5: Warm-Up Execution

Begin gradual reputation building.

Warm-Up Methods:

Manual (sending real conversations)
Automated warm-up services
Hybrid approach (recommended)

Step 6: Ramp-Up Gradually

Increase volume slowly.

Ramp Schedule:

Start: 5-10 emails per inbox daily
Increase by 20-30% every 3-5 days
Monitor deliverability at each increase
Pause if issues detected

Infrastructure Mistakes to Avoid

Using Primary Domain

Never cold email from your main business domain.

Risk:

Spam complaints damage business communications
Blacklisting affects all company emails
Recovery takes months or is impossible

Solution: Always use secondary domains for cold email.

Skipping Warm-Up

Sending high volume immediately from new domains.

Result:

Immediate spam filtering
Domain reputation destroyed
Wasted domain investment

Solution: Minimum 21-day warm-up for every new domain.

Single Inbox, High Volume

Overloading single email accounts.

Problem:

One account sending 200+ emails daily
Pattern triggers spam filters
Account suspension likely

Solution: Multiple inboxes spreading volume.

Ignoring Monitoring

Not tracking deliverability metrics.

Consequence:

Problems discovered too late
Domain reputation damage accumulates
No insight into what's failing

Solution: Daily monitoring of key metrics.

Buying Email Lists

Sending to purchased or scraped lists.

Risks:

High bounce rates destroy reputation
Spam traps guarantee blacklisting
Legal compliance issues (GDPR, CAN-SPAM)

Solution: Build organic, targeted lists.

Infrastructure Tools

Email Service Providers

Where to host your email accounts.

Recommended for Cold Email:

Google Workspace: Excellent deliverability, $6-12/user/month
Microsoft 365: Good alternative, similar pricing

Avoid for Cold Email:

Free email providers (Gmail.com, Outlook.com)
Shared hosting email providers
Cheap bulk email senders

Warm-Up Tools

Automated warm-up services.

Options:

Firstsales.io warm-up
Instantly.ai warm-up
Smartlead warm-up
Lemlist warm-up

Monitoring Tools

Track your deliverability.

Essential Tools:

Google Postmaster Tools
Microsoft SNDS
MXToolbox
Mail-Tester
GlockApps

Key Takeaways

Cold email infrastructure = technical foundation for inbox placement
Components: domains, email accounts, SPF/DKIM/DMARC, warm-up, monitoring
Use secondary domains, never primary domain for cold email
2-3 inboxes per domain, max 25-50 emails per inbox daily
Authentication required: SPF, DKIM, DMARC protocols
Warm-up minimum 21 days, gradually increase from 5-50 emails daily
Monitor daily: bounce rates (<2%), spam complaints (<0.1%), inbox placement
Proper infrastructure = 85%+ inbox placement vs. 60% without
Infrastructure is the multiplier for all other cold email investments
Avoid: primary domain, skipping warm-up, single inbox high volume
Tools: Google Workspace/Microsoft 365, warm-up services, monitoring tools

Sources:

Related Terms

CAC (Customer Acquisition Cost)

Total sales and marketing spend divided by new customers. Lower is better.

Cadence

Sequence and timing of touchpoints in outreach campaign.

Call-to-Action (CTA)

Specific action you want prospect to take. Clear CTA improves conversion.

CAN-SPAM Act

US law regulating commercial email. Requires opt-out mechanism and sender identification.