Security News > 2021 > October > Microsoft 365 will get support for custom ARC configurations
Microsoft is working on adding custom Authenticated Received Chain configuration support to Microsoft Defender for Office 365.
Enabling ARC for Office 365 hosted mailboxes prevents email authentication results from failing due to modifications made during the routing by intermediaries such as forwarding rules or mailing lists, before reaching a recipient's inbox.
"Email senders use authentication mechanisms like SPF, DKIM, DMARC to authenticate emails, but some legitimate intermediate services may potentially make changes to the email, which might cause the email to fail authentication at subsequent hop," Microsoft explains on the Microsoft 365 roadmap.
"With this change, admins will be able to add trusted intermediaries in the Microsoft 365 Defender portal to allow Microsoft to honor these ARC signatures, thereby allowing legitimate messages."
Being able to customize ARC configurations to include additional trusted intermediaries enables them to alter messages with attribution and links their signatures to their domain name, thus keeping the ARC chains intact.
Microsoft enabled ARC for all Office 365 hosted mailboxes three months later, in October 2019, to improve anti-spoofing detection within Office 365.