What is DNS (Domain Name System)?
DNS (Domain Name System) is the internet's equivalent of a phone book. It connects human-friendly domain names to the numerical IP addresses that computers use to identify each other. When sending email, DNS records act as authentication mechanisms that prove you're authorized to send messages from a particular domain.
Without proper DNS setup, your outreach emails are more likely to be flagged as spam, rejected by servers, or negatively affect your domain reputation.
Step 1: Set Up Key DNS Records
For cold email outreach, three core DNS records must be correctly configured:
1. SPF (Sender Policy Framework)
Defines which servers or services are authorized to send email on behalf of your domain.
2. DKIM (DomainKeys Identified Mail)
Provides a cryptographic signature that verifies the email's authenticity and integrity.
3. DMARC (Domain-based Message Authentication, Reporting & Conformance)
Directs how mail servers should handle messages that fail SPF or DKIM checks and allows you to receive reports.
Optional: BIMI (Brand Indicators for Message Identification)
Displays your brand logo in supported email clients and inboxes, enhancing visibility and trust.
Each of these records must be added to your domain's DNS settings using your provider's dashboard.
DNS Providers & Setup Variability
You’ll typically manage DNS settings through your domain registrar or DNS hosting provider.
Common DNS Providers:
GoDaddy
Google Domains
Namecheap
Cloudflare
Bluehost
AWS Route 53
Each provider has a different user interface for managing DNS. Some may use tabs like "Advanced DNS" or "Zone Editor" where you'll manually input TXT records. Others may offer guided DNS wizards. Always consult your provider's documentation or support center for provider-specific guidance.
Tips:
DNS changes can take up to 48 hours to fully propagate.
Only one SPF record is allowed per domain—combine entries if needed.
Double-check that each record is saved and active after configuration.
Step 2: Use Mirror Domains for Outreach
To preserve your primary domain’s sender reputation, use mirror domains (also called "burner domains") for outbound outreach.
What is a Mirror Domain? A mirror domain is a domain that looks similar to your main business domain but is used solely for sending cold emails. For example, if your domain is www.google.com, then a mirror domain could be www.google.co or www.googleco.com.
Benefits:
Protect your main domain’s reputation
Avoid blacklisting or spam penalties on your brand domain
Isolate outreach activity from core business communication
Best Practices:
Register domains that resemble your brand (e.g., alternate extensions or slight name variations)
Set up SPF, DKIM, and DMARC records for each mirror domain
Warm up each mirror domain gradually before scaling outreach volume
Step 3: Monitor & Maintain
After DNS and domain setup, it's critical to maintain ongoing visibility into performance and reputation.
Tools to Use:
DNS record validation tools (e.g., MXToolbox, DNSChecker)
Warm-up platforms (e.g., Mailreach, warmy.io)
Google Postmaster Tools for sender reputation insights
DMARC report aggregators to identify spoofing or abuse
Key Metrics:
Bounce rate
Open rate
Spam complaints
Domain reputation or blacklisting status
Common Mistakes to Avoid
Using your main company domain for cold outreach
Forgetting to configure or validate SPF, DKIM, and DMARC
Sending high volumes too quickly from new domains
Using generic or suspicious-looking domains
Not monitoring DNS health or domain reputation
Sending emails using spam trigger words
Final Thoughts
A properly configured DNS setup and thoughtful domain strategy are foundational for deliverability. Mirror domains allow you to scale safely while protecting your brand’s digital reputation.
Cold outreach is about more than messaging—your infrastructure matters. Make DNS and domain strategy a top priority, and your outreach will not only scale better, it’ll land where it’s supposed to: in the inbox.