550 Rejected by header based Anti-Spoofing policy

Version 2

    Issue Description
    Issue in delivering Marketo Email (especially for mimecast users). Email get bounced with Error: 550 Rejected by header based Anti-Spoofing policy

     

    Issue Resolution
    This error can happen if:

     

    You have not properly white listed the Marketo IPs

    You have an ssue with DKIM/SPF set up and configuration

     

    Please whitelist the set of Marketo IPs found in the doc below and make sure SPF and DKIM are set up correctly for your email domain

    https://docs.marketo.com/display/public/DOCS/Configure+Protocols+for+Marketo