mailing lists
Back in October 2019, Microsoft included ARC support in their Microsoft 365 Roadmap, stating that “[ARC] is now enabled for Office 365 hosted mailboxes.” But at that time it could only be used between Office 365 tenants, or from Microsoft’s in-house services. However in June of 2022 they made it possible for each tenant to […]
Back in October 2019, Microsoft included ARC support in their Microsoft 365 Roadmap, stating that “[ARC] is now enabled for Office 365 hosted mailboxes.” But at that time it could only be used between Office 365 tenants, or from Microsoft’s in-house services. However in June of 2022 they made it possible for each tenant to […]
ARC (Authenticated Received Chain) is an email authentication mechanism, sort of. The point of ARC is to encapsulate a check of email authentication results and include it in forwarded mail.If I receive email at an address, then I forward mail to another address, authentication results are difficult for the mail server at the second receiving site to interpret correctly. SPF works on a “last hop” methodology, meaning that a server doing an SPF check can only check the server that just connected to it — making it incompatible with email forwarding, because email forwarding involves more servers and thus more “hops.” A DKIM authentication signature is supposed to be compatible with email forwarding, but there are enough glitches out in the wild — encoding problems, rewriting headers for forwarding (or adding headers or footer text for mailing lists) that it just doesn’t work perfectly 100% of the time. And then
The Authenticated Received Chain (ARC) was designed to address situations where email messages that are forwarded, and in some cases altered, will no longer pass email authentication checks. After spending 3 years as a work item in the IETF‘s DMARC Working Group, the specification was published as RFC 8617 (HTML, PDF, plain text) on July […]