Email Security Cloud Integrated - Trusted ARC Sealer - Mar 2024

Service Update

Availability	March 13th, 2024
Product(s)	Email Security Cloud Integrated (CI)
Who's affected	Email Security Cloud Integrated (CI), Administrators

What's changing

• ARC (Authenticated Received Chain) message signing aims to retain the authentication results of messages processed by platforms such as Email Security Cloud Integrated, where otherwise, these messages would normally fail such checks. To achieve this, Mimecast must be configured as a Trusted ARC Sealer within the customers' Microsoft 365 tenant environment.
• This update will take effect immediately for any new customers from March 13, 2024, onward. Existing customer environments will be updated in accordance with the regional deployment schedule outlined in the table below.

Deployment Schedule

Region	Date
South Africa (ZA)	March 25, 2024
Canada (CA)	March 26, 2024
Australia (AU)	March 26, 2024
Germany (DE)	March 27, 2024
United Kingdom (UK)	March 27, 2024
United States (US & USB)	March 28, 2024

Recommended actions

This update will happen automatically, and customers will not need to perform any actions within Email Security Cloud Integrated or Microsoft 365 for Mimecast to be added as a Trusted ARC Sealer.

If you would like to know more about Trusted ARC Sealers, please see the Microsoft article at Trusted Arc Sealers (external link).