cPanel is introducing new experimental support for ARC (Authenticated Received Chain) for forwarded messages and mailing lists, to comply with Google’s recent email authentication requirements. This update is crucial for ensuring uninterrupted email communication for our customers using mailing lists and forwarded emails.
ARC is an authentication method designed to verify the legitimacy of forwarded emails and emails sent from mailing lists. Acting as a digital signature, ARC adds three message headers to an email: authentication results, a message signature, and a seal header.
By implementing ARC, Google aims to enhance email security and prevent spam and phishing attacks. Emails sent to Google without ARC are at risk of being marked as spam or rejected entirely, significantly impacting deliverability and communication reliability.
For more information about Google and ARC specifically, please refer to Google’s documentation.
Impact on cPanel & WHM
To maintain seamless email functionality for our users, we integrated experimental support of ARC into cPanel v122. This update ensures that your emails reach their intended recipients without issue.
Currently cPanel & WHM’s experimental ARC support only applies to outbound headers.
Please note: ARC is NOT ENABLED by default. Both DKIM and SPF must be enabled to use ARC. Review our documentation to make sure those DNS records are set up for your domains:
- Enable DKIM/SPF Globally
- Email Deliverability in cPanel (per domain DKIM/SPF management)
Once DKIM and SPF are enabled, you can log into WHM and navigate to Service Configuration > Exim Configuration Manager > Basic Editor > Mail tab to enable ARC signing to outgoing mail. Here is an example of what those ARC headers look like on a message sent from a cPanel mail server:
cPanel is dedicated to providing a smooth transition for our users and maintaining the reliability of our email platform. We encourage our users to evaluate if ARC support is compatible with their current mailing list or email forwarding setup for uninterrupted delivery.
