Cold Email DNS Configuration: Complete 2026 Technical Guide
By Puzzle Inbox Team · May 14, 2026 · 11 min read
DNS configuration determines cold email deliverability. Here is the complete guide to SPF, DKIM, DMARC, MX, and related records for cold email.
DNS Configuration for Cold Email
DNS configuration is the invisible foundation of cold email deliverability. Misconfigured DNS drops reply rates 30-50%. Properly configured DNS enables Google Workspace and Outlook 365 to inherit their established IP reputation for your cold email. Here is the complete technical guide.
Required DNS Records for Cold Email
- MX records: Mail exchange for receiving replies
- SPF (TXT): Sender Policy Framework authorization
- DKIM (TXT): DomainKeys Identified Mail signing
- DMARC (TXT): Domain-based Message Authentication policy
- A records: For tracking subdomain (if using custom tracking)
SPF Record for Cold Email
SPF tells receiving servers which servers are authorized to send from your domain.
For Google Workspace cold email: v=spf1 include:_spf.google.com ~all
For Microsoft 365 cold email: v=spf1 include:spf.protection.outlook.com ~all
Critical SPF limits: Maximum 10 DNS lookups. Use SPF flattening if exceeding.
DKIM Record for Cold Email
DKIM adds cryptographic signature to each email. For Google Workspace: Google generates DKIM key in Admin Console. Publish public key as TXT record in DNS. Signing domain must match From domain for DMARC alignment.
For Outlook 365: DKIM generated in Microsoft 365 admin center. Publish CNAME or TXT records as provided.
DMARC Record for Cold Email
DMARC ties SPF and DKIM together.
Recommended DMARC progression:
- v=DMARC1; p=none; rua=mailto:dmarc@yourdomain.com (monitoring)
- v=DMARC1; p=quarantine; rua=mailto:dmarc@yourdomain.com (after 2-4 weeks)
- v=DMARC1; p=reject; rua=mailto:dmarc@yourdomain.com (after successful p=quarantine)
MX Records for Cold Email
Google Workspace MX:
- Priority 1: aspmx.l.google.com
- Priority 5: alt1.aspmx.l.google.com
- Priority 5: alt2.aspmx.l.google.com
- Priority 10: alt3.aspmx.l.google.com
- Priority 10: alt4.aspmx.l.google.com
Microsoft 365 MX:
- Priority 0: yourdomain-com.mail.protection.outlook.com
Custom Tracking Domain DNS
For tracking domain (e.g., track.yourdomain.com):
- CNAME record pointing to sending platform tracking domain
- Platform-specific value (e.g., track.instantly.ai)
DNS Verification Tools
- MXToolbox — Free DNS record lookup
- Google Admin Console — Built-in DNS status
- Microsoft 365 Admin — MX/DKIM verification
- DMARC reporting tools (EasyDMARC, Dmarcian)
Common DNS Configuration Errors
- SPF exceeding 10 DNS lookups (silent failure)
- DKIM signing with wrong domain (breaks DMARC alignment)
- DMARC staying at p=none forever (misses hardening)
- MX records missing or pointing to wrong servers
- Tracking subdomain not configured (affects link tracking)