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
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