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Error '550-5.7.26 Unauthenticated email from *recipient's domain* is not accepted' in Email Log

Publish Date: Aug 8, 2023
Description
The user is getting this permanent error in the email log:

550-5.7.26 Unauthenticated email from *recipient's domain* is not accepted due to \r\n550-5.7.26 domain's DMARC policy. Please contact the administrator of \r\n550-5.7.26 *recipient's domain* domain if this was a legitimate mail. Please visit \r\n550-5.7.26.
Resolution

Domain-based Message Authentication, Reporting & Conformance or what we call DMARC, is an email authentication method that uses Sender Policy Framework (SPF) and DomainKeys identified mail (DKIM) to determine the authenticity of an email message. 

Since DMARC relies on the established SPF and DKIM standards for email authentication, errors regarding DMARC can be due to missing SPF and/or DKIM. 

Make sure that the sender's domain already has SPF and DKIM setup. 

See:
Create a DKIM Key
Sender Policy Framework and Salesforce SPF Records
Knowledge Article Number

000391969

 
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