ARC

ARC is a chain of signatures that are added to the email to indicate the state of the email as it is processed by each mail server along its route.

When Mailcast receives an email, it does a full range of checks including SPF, DKIM, and DMARC. The results of those checks are added to the email as part of an ARC chain before it is forwarded on.

Those processing results are also made available when the email is delivered via a webhook.