Are you ready for New Email Threading Behavior?

I know… I know. I started asking that same question back in 2022. At the time, the new threading behavior was a promising improvement over Ref Ids, but there were still too many unresolved edge cases.

As a result of these concerns, Salesforce pushed out the enforcement date (several times) and set out to address these concerns. Now here we are, 2 years later. Is Salesforce ready? I believe the answer is Yes. Now, the question remains. Are you ready for the New Email Threading Behavior?

What’s Changing?

Email threading organizes an email conversation into a continuous thread. In a Salesforce case context, email threading ensures inbound and outbound emails related to a specific case are correctly associated to that case record.

Ref ID Threading

Prior to Winter ’21, email threading was accomplished with Ref ID Threading. A ref ID is a string (containing the Salesforce organization id and the case id) that is embedded in the email subject, body, or subject and body. Incoming emails are inspected and associated to existing cases based on the Ref ID.

Email Header Based Threading

In Winter ’21, email header based threading was introduced. Email header based threading leverages the email header (specifically attempting to find a match between the email header In-Reply-To variable and the Message Id contained in an existing Email Message records) to associate an email to an existing case.

There are a number of advantages to an email header vs a string based approach. However, there are also gaps. Some of the most frequently cited include:

  • This approach requires an Email Message record (with the corresponding Message ID populated) and a custom apex action (to embed the references Message Id).
  • Some email servers strip email headers.
  • This approach removes the ability to forward an unassociated email to an existing case.

Lightning Threading

In Spring ’23, lightning threading was introduced. Lightning threading (like Ref ID threading) is a formatted string that can be embedded into the email subject, body, or both subject and body. Lightning thread and email header threading work in combination to associate the email to an existing case.

With this final piece of the puzzle in place, enforcement is planned for Spring ’25.

Transition to New Email Threading Enforced Spring ’25

With this final piece of the puzzle in place, enforcement is planned for Spring ’25. It seems unlikely that the date will be moved again…. but I’m not making any bets.

So I ask again…..

Are you ready for the New Email Threading Behavior?

If you have a vanilla implementation, you should be ready to go. The transition should be seamless.

If you have customizations around your case and/or email process, it’s time to take stock and develop a plan.

Take Stock

  • Have you implemented a custom apex email service?
    • Does the apex email service expect a Ref ID?
    • Does the apex email service include any other logic that may be impacted?
  • Have you implemented a Ref ID formula field?
    • Is that formula field used to in any matches processes?
    • Is that formula field used in any email templates?
    • Is that formula field used in any automation?
  • Have you implemented email templates?
    • Do those email templates include the Ref ID?
  • Have you implemented custom email, auto-response rules, etc. which contain a Ref ID?
  • Do you have any automation generating emails related to the case or email message object?
    • Does that automation include Ref Id?
  • Are there additional opportunities to optimize existing logic around email threading?
  • Have you tested for potential impact?
    • Do you understand what happens when an outgoing email (sent with Ref ID), is returning as an inbound email (with the new email threading behavior enabled?
  • Is there a rollover plan in place?