Email infrastructure for cold email

# Email infrastructure for cold email

Email infrastructure is the technical foundation of cold email deliverability. Without proper domain setup, authentication, and inbox configuration, even the best messaging will fail to reach inboxes. This lesson covers the essential technical components you need to establish and maintain.

Key Takeaways

- Proper infrastructure is non-negotiable for deliverability

- Use dedicated domains and inboxes for cold email

* - Implement SPF, DKIM, and DMARC authentication * - Warm up domains gradually before scaling

Domain strategy

Dedicated vs. shared domains

Dedicated domains:

• Purchased specifically for cold email
• Full control over reputation
• No risk to primary business domain
• Essential for scale

Shared domains:

• Using your primary business domain
• Risk to main business reputation
• Limited sending capacity
• Not recommended for cold email

Recommendation: Always use dedicated domains for cold email. Purchase domains that relate to your brand but are separate from your primary domain (e.g., use `getcompany.com` if your main domain is `company.com`).

Domain portfolio

For testing:

• 1-2 domains
• Single inbox per domain
• 20-50 emails per day
• Focus on learning and validation

For scale:

• 5-10 domains minimum
• Multiple inboxes per domain
• 100-500+ emails per day total
• Distributed sending across portfolio

Domain selection criteria:

• Age (older domains are better)
• Clean history (no previous spam issues)
• Brand relevance (trustworthy extension)
• Geographic alignment (match target region)

DNS authentication

SPF (Sender Policy Framework)

What it does: SPF specifies which mail servers are authorized to send email from your domain. It prevents spammers from sending from your domain.

Setup: ```txt v=spf1 include:sendgrid.net -all ```

Best practices:

• Keep SPF records under 10 DNS lookups
• Use "include" for third-party services
• End with "-all" for strict policy
• Test with SPF record validators

DKIM (DomainKeys Identified Mail)

What it does: DKIM adds a cryptographic signature to your emails, allowing receiving servers to verify that the email hasn't been tampered with during transit.

Setup:

• Generate DKIM keys through your email provider
• Add public key to DNS as TXT record
• Configure signing in your email platform
• Verify with DKIM validators

Best practices:

• Use 1024-bit or 2048-bit keys
• Rotate keys periodically (every 6-12 months)
• Monitor for authentication failures
• Keep private keys secure

DMARC (Domain-based Message Authentication)

What it does: DMARC builds on SPF and DKIM to tell receiving servers how to handle emails that fail authentication. It also provides reporting.

Setup: ```txt v=DMARC1; p=quarantine; rua=mailto:dmarc@yourdomain.com ```

Policy levels:

• `p=none` - Monitor only (start here)
• `p=quarantine` - Send to spam folder
• `p=reject` - Block failed emails

Best practices:

• Start with `p=none` for monitoring
• Gradually move to `p=quarantine`
• Only use `p=reject` after full validation
• Review DMARC reports regularly

Inbox configuration

Dedicated inboxes

Why dedicated inboxes:

• Full control over sending limits
• No interference with business email
• Better deliverability monitoring
• Scalable architecture

Setup requirements:

• Create through your email provider
• Use professional naming (outbound@domain.com)
• Configure forwarding for responses
• Set up IMAP for monitoring

Inbox rotation

Single inbox approach:

• Easier to manage
• Limited by provider limits
• Single point of failure
• Suitable for low volume

Multiple inbox approach:

• Distributes sending volume
• Reduces risk per inbox
• More complex management
• Required for high volume

Rotation strategy:

• Use 3-5 inboxes per domain
• Rotate sending across inboxes
• Monitor each inbox individually
• Replace underperforming inboxes

Technical configuration

IP addresses

Shared IPs:

• Provided by email service providers
• Reputation shared with other users
• Lower cost
• Suitable for most use cases

Dedicated IPs:

• Exclusive to your sending
• Full control over reputation
• Higher cost
• Required for very high volume

Recommendation: Start with shared IPs. Move to dedicated IPs only when sending 50,000+ emails per day and you have established sending patterns.

Email service providers

Considerations:

• Deliverability features
• Warm-up capabilities
• Analytics and reporting
• API access
• Cost structure

Popular providers:

• SendGrid, Mailgun (general purpose)
• Amazon SES (cost-effective at scale)
• Postmark (focus on deliverability)
• Specialized cold email platforms

Domain warm-up

Warm-up process

Week 1:

• 10-20 emails per day
• High-quality, engaged recipients
• Monitor bounce and spam rates
• Focus on establishing reputation

Week 2-3:

• Increase to 30-50 emails per day
• Maintain high engagement
• Expand to safe lists
• Continue monitoring

Week 4+:

• Gradually increase to target volume
• Maintain engagement quality
• Scale across multiple inboxes
• Ongoing reputation monitoring

Warm-up best practices

Engagement focus:

• Send to known contacts first
• Encourage replies and interactions
• Avoid cold lists during warm-up
• Monitor feedback loops

Volume pacing:

• Increase gradually (10-20% per week)
• Don't skip warm-up for speed
• Pause if issues arise
• Document your warm-up timeline

Monitoring and maintenance

Deliverability monitoring

Key metrics:

• Inbox placement rate
• Bounce rate (keep under 2%)
• Spam complaint rate (keep under 0.1%)
• Open rate (benchmark for engagement)

Monitoring tools:

• Google Postmaster Tools
• Microsoft SNDS
• Provider analytics dashboards
• Third-party deliverability tools

Regular maintenance

Monthly tasks:

• Review DMARC reports
• Check blacklist status
• Analyze engagement metrics
• Clean email lists

Quarterly tasks:

• Rotate DKIM keys
• Review domain portfolio
• Audit authentication records
• Update warm-up documentation

Common mistakes to avoid

Skipping warm-up: Sending at full volume immediately will trigger spam filters and damage your domain reputation. Always warm up new domains gradually.

Using personal email accounts: Gmail, Outlook, and other personal email providers have strict sending limits and terms of service that prohibit cold email. Use dedicated business infrastructure.

Ignoring authentication: SPF, DKIM, and DMARC are not optional. Without proper authentication, your emails will be flagged as suspicious or rejected outright.

Neglecting monitoring: Infrastructure requires ongoing attention. Set up monitoring alerts and review metrics regularly to catch issues before they become problems.

Conclusion

Email infrastructure is the unsung hero of cold email success. Invest time in proper setup, authentication, and warm-up, and your campaigns will have the technical foundation needed to reach inboxes consistently.

Your next step should be to learn about email analytics to measure and optimize your infrastructure performance.