What is a CNAME record?

A CNAME (Canonical Name) record is a type of DNS entry that points a domain name to another domain instead of an IP address. For email marketing professionals, mastering CNAME records is essential: they allow for tracking domain personalization, delegated DKIM authentication, and sending reputation isolation. According to MailerSend data (2025), a correctly configured CNAME can improve inbox placement rates by 15 to 25% by avoiding generic tracking links flagged by spam filters.

What is a CNAME Record?

A CNAME record works as a DNS alias: it redirects a domain name to another domain name (not an IP address). Unlike an A record that points directly to an IP address, the CNAME establishes a reference relationship. When you query tracking.yourdomain.com configured as a CNAME to links.mailprovider.com, the DNS first resolves the CNAME and then retrieves the final IP of the target domain.

The main advantage: if the provider changes its IP infrastructure, your CNAME continues to function automatically without intervention. This is crucial for ESPs (Email Service Providers) like SendGrid, Mailchimp, Brevo, or ActiveCampaign who regularly modify their servers.

Syntax of a CNAME record:

tracking.yourdomain.com. IN CNAME links.esp-provider.com.

Warning: a CNAME cannot coexist with other records (MX, TXT, NS) on the same domain name. This technical constraint explains why you cannot use a CNAME on a root domain (example.com) that hosts MX records to receive emails.

CNAME for Email Marketing: 3 Essential Uses

CNAME records transform email deliverability by enabling domain personalization, delegated authentication, and reputation isolation. These three applications reduce spam signals and strengthen trust from receiving servers.

Personalized Tracking with Brand Subdomains

ESPs use generic tracking domains by default (links.brevo.com) to redirect clicks. These third-party URLs trigger alerts with Gmail, Outlook, and spam filters. By setting up a custom tracking CNAME (e.g., track.yourdomain.com), you replace these generic links with your own domain.

Measured impact according to Mailersend (2025): +18% inbox placement rate and +22% click rate thanks to domain recognition by recipients. Receiving servers associate the tracking domain with your sending domain, enhancing brand consistency and reputation.

Configuration example for SendGrid:

em123.yourdomain.com CNAME u12345.wl.sendgrid.net

For Mailchimp, you typically create:

track.yourdomain.com CNAME track.mailchimp.com

Delegated DKIM Authentication via CNAME

The DKIM (DomainKeys Identified Mail) record authenticates your emails with a cryptographic signature. Traditionally published in TXT, DKIM can be delegated via CNAME to your ESP, which automatically manages key rotation. This method simplifies maintenance: when SendGrid or Mailchimp renews their DKIM keys every 6-12 months, no manual intervention is needed.

Microsoft 365 and Google Workspace recommended this approach since 2024. SendGrid generates two DKIM selectors (s1 and s2) configured as follows:

s1._domainkey.yourdomain.com CNAME s1.domainkey.u12345.wl.sendgrid.net
s2._domainkey.yourdomain.com CNAME s2.domainkey.u12345.wl.sendgrid.net

According to Cloudflare (2025), this configuration reduces authentication errors related to expired DKIM keys by 40%. The CNAME allows the ESP to control the public key while you retain ownership of the domain.

Dedicated Subdomains for Reputation Isolation

Separating your transactional emails (order confirmations, password resets) from your marketing campaigns via distinct subdomains protects your sending reputation. If a promotional campaign generates spam complaints, only the marketing subdomain is penalized.

Recommended architecture:

• Transactional: mail.yourdomain.com (CNAME to transactional ESP like Postmark, Mailgun)
• Marketing: news.yourdomain.com (CNAME to marketing ESP like Brevo, Mailchimp)
• Notifications: alerts.yourdomain.com (dedicated CNAME)

Data from Return Path (2024) shows that senders using isolated subdomains maintain an average sender score of 92/100 compared to 78/100 for those mixing all types of sending. This segmentation improves email deliverability by 15 to 30% depending on sending volume.

Setting Up a CNAME Record in 4 Steps

The configuration requires access to your DNS zone (at your registrar such as OVH, Gandi, Namecheap, or via Cloudflare) and information provided by your ESP.

Step 1: Retrieve CNAME values from your ESP
Log in to SendGrid, Mailchimp, Brevo, or your platform. Go to the “Domain Authentication” section. The tool automatically generates the necessary CNAME records (tracking, DKIM, sometimes SPF).

Step 2: Access your DNS manager
Identify where your DNS zone is hosted (often at the domain’s registrar). Look for the “DNS Management,” “DNS Zone,” or “DNS Records” section.

Step 3: Create the CNAME records
Add each record with:
– Name/Host: the subdomain (e.g., track, s1._domainkey)
– Type: CNAME
– Value/Target: the target domain provided by the ESP
– TTL: 3600 (1 hour) or leave default

Step 4: Verify DNS propagation
Use MXToolbox, DNSChecker, or WhatsMyDNS to confirm the CNAME is active. DNS propagation usually takes 15 minutes to 48 hours depending on global DNS servers. Mailchimp and SendGrid offer integrated verification tools that automatically test your records.

Common errors to avoid:

• Forgetting the trailing dot in the CNAME value (some DNS require it: target.com.)
• Creating a CNAME on the root domain (example.com) while MX records already exist

Impact on Email Deliverability

Well-configured CNAME records directly contribute to deliverability metrics. According to a Validity study (2025) covering 2 million sending domains, senders using customized CNAMEs for tracking and DKIM achieve:
– +15 to 25% inbox placement rate (inbox vs spam)
– +12 points increase in average sender score (88 vs 76/100)
– -35% bounce rate related to authentication

Three essential best practices:

• Gradually warm-up new subdomains: start with 500 emails/day for 2 weeks before increasing volume (Gmail and Outlook penalize sudden spikes)
• Monitor DNS records: check monthly with MXToolbox, DNSChecker, or Google Search Console to ensure CNAMEs remain valid
• Combine CNAME with SPF and DMARC: complete authentication (SPF + DKIM + DMARC) reduces spam reports by 60% according to PowerDMARC (2025)

For e-commerce professionals and marketers sending over 50,000 emails/month, investing in a professional CNAME setup (2-4 hours of initial setup) generates measurable ROI through improved email conversion rates.

Secure Your Deliverability with CaptainVerify

An optimal CNAME setup is not enough if your list contains invalid addresses or spam traps. Hardbounces degrade your sender score regardless of DNS authentication. CaptainVerify validates your email lists in real-time (syntax, domain, mailbox) with 99.2% accuracy, ensuring only valid contacts receive your campaigns. Combined with properly configured CNAME records, this dual protection maximizes your inbox placement rate. Test 100 validations for free to measure the impact on your deliverability.