How we resolved Constant Contact authentication issues and investigated email spoofing in WordPress

Email deliverability and security often extend beyond WordPress itself. When issues arise, they typically involve DNS configuration, third-party platforms, and email providers working together.

In this case, the challenge involved two related problems: Constant Contact emails sending from an incorrect domain and ongoing concerns about email spoofing.

Issue Background

After importing a large contact list into Constant Contact, the account was temporarily flagged and emails began sending from a fallback domain instead of the intended branded domain.

At the same time, there were reports of emails appearing to be sent from internal addresses, raising concerns about spoofing.

Diagnosis

Constant Contact domain not authenticated

Emails were being sent from a fallback domain because DKIM authentication was not configured. This is required for Constant Contact to send from a branded domain.

Missing DNS records

The required DNS records included:

ctct1._domainkey → dkim1.ccsend.com
ctct2._domainkey → dkim2.ccsend.com
_dmarc → v=DMARC1; p=none;

Without these records, email providers could not verify domain ownership.

Email spoofing was external

Header analysis showed SPF, DKIM, and DMARC failures, confirming that spoofed emails were sent from unauthorized servers and not from the website.

DMARC policy too permissive

The existing DMARC policy used p=none, which only monitors failures and does not block spoofed emails.

Resolution Steps

Add and verify DNS records

The required DKIM and DMARC records were added and verified through DNS propagation and Constant Contact validation.

Strengthen DMARC policy

v=DMARC1; p=quarantine; sp=quarantine; adkim=s; aspf=s; pct=100;

This change helps route failed authentication emails to spam instead of inboxes.

Review SPF configuration

v=spf1 include:spf.protection.outlook.com -all

This ensures only authorized servers can send emails on behalf of the domain.

Validate DKIM across services

DKIM was confirmed for Constant Contact and the primary email provider to ensure proper authentication across platforms.

Confirm spoofing via header analysis

Email headers were analyzed to verify sending sources and confirm the issue was external spoofing rather than a website vulnerability.

DNS troubleshooting checklist

• Verify DKIM records: Ensure CNAME records (e.g., ctct1._domainkey, ctct2._domainkey) resolve correctly and match provider values.
• Check DMARC policy: Confirm a valid TXT record exists at _dmarc and consider moving from p=none to p=quarantine or p=reject after testing.
• Validate SPF: Ensure only legitimate senders are included and the record ends with -all (or ~all during testing).
• Avoid multiple SPF records: Combine includes into a single SPF record to prevent failures.
• Check DNS propagation: Use tools to confirm records are live globally before testing email sending.
• Review TTL values: Lower TTL during changes to speed up propagation when troubleshooting.
• Confirm provider verification: Make sure services like Constant Contact show the domain as “authenticated.”

How to analyze email headers with MXToolbox

When diagnosing spoofing or deliverability issues, reviewing full email headers is essential. MXToolbox provides an easy way to interpret these results.

Step 1: Get full email headers

• In Gmail: open the email and click “Show original”
• In Outlook: open message options and view “Internet headers”

Step 2: Paste into MXToolbox

• Go to MXToolbox Email Header Analyzer
• Paste the full header data
• Run the analysis

Step 3: Review authentication results

Focus on these key indicators:

• SPF: Should show pass for authorized sending IPs
• DKIM: Should show pass with a valid signature
• DMARC: Should align with SPF or DKIM and pass policy checks

Step 4: Identify spoofing signals

• SPF = fail
• DKIM = none or fail
• DMARC = fail
• Sending IP does not match your email provider

If these appear together, the message is almost certainly spoofed and not sent from your system.

Final Outcome

After implementing the changes, Constant Contact emails were properly authenticated and sent from the correct domain. Spoofed email visibility was reduced through stronger DMARC enforcement.

The WordPress site and hosting environment were confirmed to be secure and not responsible for the spoofed emails.

If you are dealing with email authentication issues, spoofing concerns, or DNS configuration challenges, our team can help.

Contact Freshy