Enhance Security with a New Threading Behavior for Email-To-Case

A new Email-to-Case threading behavior matches incoming emails with their header information instead of through a Ref ID from the subject or body. New outbound emails don’t contain a Ref ID.

Where: This change applies to Lightning Experience in Professional, Enterprise, Essentials, Unlimited, Performance, and Developer Editions.

How: New orgs default to this new threading behavior. Admins for existing orgs can turn the new behavior on or off with a Release Update, until Salesforce enforces the update in the Winter '22 release. Existing orgs continue to work based on ref ID until the new behavior is enabled, to give admins time to try out the new functionality before the enforcement date.