Understanding Constant Contact Email Authentication
Constant Contact enables businesses to send newsletters and promotional campaigns. Custom domain authentication prevents "via constantcontact.com" sender headers and guarantees full DMARC compliance.
When Constant Contact delivers outbound emails on your behalf, recipient mail transfer agents (MTAs) at Google, Yahoo, Microsoft, and corporate mail gateways inspect the sender identity. Without a published SPF record explicitly permitting Constant Contact's IP ranges, these emails trigger SPF Softfail (~all) or Hardfail (-all), severely degrading domain reputation and inbox placement.
Required DNS Records for Constant Contact
Publish the following DNS records in your domain registrar or DNS management console (Cloudflare, AWS Route 53, GoDaddy, Namecheap):
| Type | Host / Name | Value / Target | TTL | Purpose |
|---|---|---|---|---|
| TXT | @ | v=spf1 include:spf.constantcontact.com ~all | 3600 | Constant Contact SPF. |
| TXT | ctct._domainkey | v=DKIM1; k=rsa; p=MIGfMA0GCSqGSI... | 3600 | Constant Contact DKIM key. |
Step-by-Step Setup Instructions
In Constant Contact > My Account > Settings > Email Authentication.
Select "Self-Publish Authentication" and enter your sender domain.
Copy the DKIM TXT record and add it to your DNS zone.
Add "include:spf.constantcontact.com" to your root SPF record.
Click Verify in Constant Contact.
Common Constant Contact SPF Configuration Mistakes
× DMARC Quarantine on Newsletters
Cause: Sending from free webmail (gmail/yahoo) or unauthenticated domain.
Fix: Authenticate custom business domain.
Frequently Asked Questions
What is the SPF include string for Constant Contact?
Use "include:spf.constantcontact.com".
What does DMARC Quarantine on newsletter campaigns indicate?
If your Constant Contact campaigns land in the DMARC quarantine folder, it typically means you're sending from a free webmail address (e.g. yourname@gmail.com) or your custom domain is not authenticated in Constant Contact. DMARC quarantine routes unaligned mail to the spam folder rather than the inbox.
What is Constant Contact Self-Publish Authentication?
Constant Contact's Self-Publish Authentication feature allows you to generate DKIM keys within the Constant Contact dashboard and publish them directly in your DNS zone. This creates a DKIM signature aligned with your custom domain, satisfying DMARC requirements.
What DKIM selector does Constant Contact use?
Constant Contact generates a TXT DKIM record with the selector "ctct" (Constant Contact), published at ctct._domainkey.yourdomain.com. The full key is provided in the Email Authentication settings panel.
Does Constant Contact meet the 2024 Gmail bulk sender requirements?
Yes, provided you authenticate your custom sending domain with SPF (include:spf.constantcontact.com), DKIM (ctct._domainkey TXT), and DMARC (v=DMARC1; p=reject or p=quarantine). Without authentication, campaigns sent to Gmail addresses exceeding 5,000/day will be rejected.
How do I verify my Constant Contact SPF and DKIM are working?
Use IncogSay's SPF Checker to confirm include:spf.constantcontact.com is in your DNS TXT record. Use the DKIM Checker with your domain and the selector "ctct" to verify the TXT record is published and the key parses correctly.