The check-auth@verifier.port25.com email address is a tool provided by Port25 (now a part of SparkPost) for testing and verifying your email authentication configuration, including SPF, DKIM, and DMARC records.

When you send an email to this address, you will receive a detailed report back about your email authentication setup. This is helpful for diagnosing configuration issues and ensuring proper email deliverability.

How to Use check-auth@verifier.port25.com

1

Set Up Your Email Client

  • Use your preferred email client or script to send an email from your domain.
  • Ensure the email is sent from the server/domain you want to test.
2

Compose an Email

  • To: check-auth@verifier.port25.com
  • Subject: (Can be left blank or set to something descriptive, e.g., "SPF/DKIM Test")
3

Send the Email

Simply send the email without adding attachments or extra content.

4

Receive the Report

Within a few minutes, you will receive a reply to the "From" address with a detailed report of the email authentication results.

What the Report Includes

The returned report contains tests and results for the following:

  1. SPF (Sender Policy Framework)
    • Verifies if the IP address sending the email is authorized to send on behalf of the domain.
    • Example output:
      • SPF check: pass
  2. DKIM (DomainKeys Identified Mail)
    • Verifies if the email has a valid DKIM signature and matches the public key in your DNS records.
    • Example output:
      • DKIM check: pass
  3. DMARC (Domain-based Message Authentication, Reporting & Conformance)
    • Ensures alignment between the From domain and the SPF/DKIM results.
    • Example output:
      • DMARC check: pass
  4. HELO/EHLO String Check
    • Checks if the SMTP HELO/EHLO hostname complies with RFC standards.
  5. Additional Tests
    • Reverse DNS (rDNS) validation.
    • Authentication-Results header validation.

Example Report Snippet

===========================================================
Summary of Results
===========================================================
SPF check: pass
DKIM check: pass
DMARC check: pass
HELO check: pass
rDNS check: pass
===========================================================

Troubleshooting Common Issues

Issue Solution
SPF Fail Ensure your SPF record includes all authorized mail servers:
v=spf1 include:_spf.google.com include:mailgun.org -all
DKIM Fail
  • Verify that your DKIM TXT record is published in DNS.
  • Ensure the selector matches the one used in your emails.
DMARC Fail Publish a DMARC TXT record in DNS:
_dmarc.example.com IN TXT "v=DMARC1; p=none; rua=mailto:dmarc-reports@example.com"
rDNS Fail Ensure the sending IP address has a reverse DNS (PTR) record matching your domain.

Best Practices

  1. Use Tools for Diagnostics:
  2. Test After DNS Changes:
    • Whenever you update SPF, DKIM, or DMARC records, test again to confirm proper propagation and functionality.
  3. Check Email Headers:
    • Look at the email headers for Authentication-Results to identify any issues.