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".