The ESPC feels that email authentication is critical for establishing and maintaining email credibility and accountability. In fact, adoption of email authentication is mandatory for ESPC members.

To encourage adoption by ALL senders, The ESPC has partnered with ESPC member Port25 to provide this testing tool. The tool allows you to check the format of any DKIM, DomainKey, SenderID or SPF records published by your domain and to see the result of these authentication checks on any message you send.

To use the tool, simply send an email from the domain you want to test to check-auth@verifier.port25.com. You will receive a return email containing an analysis of the authentication status of the message you sent.

Authentication Resources

About SenderID & SPF:
Domain owners must identify their sending mail servers by IP Address in new DNS records. Receivers verify the Purported Responsible Address (PRA) against the information stored in DNS to reject unauthorized messages. SenderID is the evolution of the Sender Permitted From (SPF) proposal developed by Meng Weng Wong and the CallerID proposal developed by Microsoft.

For more information on SenderID and SPF, check the following links:


Sender ID Wizard:
Create SPF records for your domain:

About DomainKeys and DKIM:
Domain owners must include a digital signature in outgoing messages and publish their public key in new DNS record. Receivers verify the signature against the public key available in DNS to reject unauthorized messages. DomainKeys was developed by Yahoo!. DKIM is a synthesis and enhancement of Yahoo!'s DomanKeys and Cisco's Identified Internet Mail specifications.

For more information on DomainKeys and DKIM, check the following links:


DKIM Wizard:
Create DKIM records for your domain: https://www.port25.com/dkim-wizard/

Support / Questions:

If you experience any problems or have any questions about the testing tool, please send us an email.

ESPC Email Verification Tool powered by Port25