How Email to Case Premium Handles Email Threading

 

Email to Case Premium uses a "Yes, and..." approach to threading, accounting for all of the (below-listed) changes made by Salesforce and retaining a fallback mechanism. This ensures that emails are correctly related to existing cases and prevents creating unnecessary duplicate cases.

 

If the Email to Case Premium inbound routing address cannot find a Message-ID in the In-Reply-To email header, it looks for additional references of the originating email message. Then, Email to Case Premium will look for a Lightning Thread Token. Finally, Email to Case Premium uses the E2CP Thread ID field in the subject or body of the email message.

 

As of version 9.18 of Email to Case Premium, the order of operations for matching inbound emails to their associated open Cases is as follows:

1. In-Reply-To email header 
2. References in email header 
3. Outlook-specific 'Thread-Index' email header 
4. Lightning Thread Token (if enabled) 
5. Legacy E2CP Thread ID (E2CP__Case_Thread_Id__c)

 

Items 1 - 3 above account for the Message-ID Threading behavior introduced by Salesforce in Winter '21. 

Email to Case Premium will look for matching threading information in the email headers of the email messages to correctly thread them to their related Cases. Email to Case Premium looks for the Message-IDs, which are stored in the MessageIdentifier field for Email Messages in Salesforce. As back-and-forth communication happens and replies come into Salesforce, Email to Case Premium will look at the In-Reply-To and References email headers to thread them to the appropriate Case.  Email to Case Premium also looks for the Thread-Index email header, used with specific email services such as Outlook.  This is stored in the 'ClientThreadIdentifier' field for Email Messages in Salesforce.  For more information on how Salesforce uses this header, please see https://developer.salesforce.com/docs/atlas.en-us.apexref.meta/apexref/apex_System_Cases_getCaseIdFromEmailHeaders.htm

 

Item 4 accounts for the Lightning Threading behavior introduced in Winter '24, where email messages are matched to the correct case using a secure token present in the subject or body of emails, no longer relying on Message-IDs, In-Reply-To email headers, and/or References being present in the email headers. Email threading tokens are a unique 23-character string formatted with a prefix and suffix, for example, thread::pp5XPGfmNf2hRZdRCWnrohc::.  You would want to ensure that this setting is enabled and that you see Case.Thread_Token within your email templates (ideally in both the subject and the body).  It is considered best practice, by both Vicasso and Salesforce, to use the new Lightning thread token in both the subject and email body, but if you'd rather use it in just one location, please choose the subject.

 

Item 5 acts as a fallback if all prior mechanisms for threading fail to work. Here, Email to Case Premium looks for the packaged E2CP Case Thread ID by searching the email message's Subject, Text Body, and HTML Body fields. Some considerations for this method are:

• If a Case matching the Thread ID in the subject is found, then that case is selected, and all other Thread IDs are ignored.
• If multiple Thread IDs are found, the Thread ID matching the newest Case will be used.
• If no Thread IDs are found at all in the email, this will result in a new Case being created.

 

 

Frequently Asked Questions (FAQ):

• Does Email to Case Premium Support Salesforce's Message-Id Threading?
  • Yes! As of version 8.49, E2CP works seamlessly with the new Message-Id Threading behavior introduced by Salesforce, as long as EmailMessage.MessageIdentifier is getting populated.
• Does Email to Case Premium support Salesforce's Lightning Threading?
  • Yes!  As of version 9.18 of Email to Case Premium, Lightning Threading is fully supported.
• Limitations of iOS Mail App
  • Due to the fact that Apple fails to adhere to established email header standards if a user does not use an email template that includes the required reference or thread ID (such as E2CP__Case_Thread_Id__c or Case.Thread_Token), Email to Case Premium will not have the necessary identifier to ensure replies are threaded to the correct case if the reply comes in from iOS Mail.
• Limitations of the Lightning Threading Token
  • Lightning Threading Token can be used with either Lightning Templates and Classic Email Templates, but with some limitations.  For Classic Email Templates, the Lightning Threading Token can be used in Text and HTML template types, not for Visualforce template type (which is what Email to Case Premium packages).

 

Salesforce's history regarding email threading, as noted in this article:

 

• Summer '20: In this release, Salesforce automatically saves the Message-ID of all standard emails sent and received by Email-to-Case.
• Winter '21: All new orgs default to the email header-based threading mechanism, and Ref ID-based threading is no longer recommended. Please refer to this article for more information.
• Summer '21: Email header-based threading is supported for case email alerts sent by Flows or Process Builder processes.
• Winter '23: Email alerts contain information to identify the related case in the Message-ID, regardless of whether or not header-based threading is enabled.
• Spring '23: All new orgs default to Lightning threading. Lightning threading is now the recommended approach and includes a merge field and Apex methods, similar to Ref ID.
• Winter '24: Salesforce announces that Lightning threading will be enforced in the Spring '25 release. Please refer to this article for more information.
• Spring '24: Salesforce enables a new header-based threading preference, allowing customers to choose how emails are threaded.
• Spring '25: The Disable Ref ID and Transition to New Email Threading Behavior release update is scheduled to be enforced.  Salesforce no longer plans to enforce the Disable Ref ID and Transition to New Email Threading Behavior release update, but it is still strongly encouraged that everyone make the transition.

 

Please note: threading behaviors may act unexpectedly if Forward to Case is being utilized.

For questions or assistance, please open a Support Case with Vicasso by emailing e2cpremium@vicasso.com.