Email Responses Are Not Added to the Case in Salesforce Email-to-Case

Overview

Email-to-Case (E2C) relies on a thread ID mechanism to match incoming customer replies to the correct Salesforce Case. The following steps verify that Email-to-Case is configured correctly so that customer responses are automatically attached to and visible on the Case record.

Step 1: Verify Email Threading Settings

The thread ID must be added to either the email subject line or the email body (or both). Adding it to both provides a backup if the customer removes the thread ID from one location.

1. Navigate to Setup.
2. In Quick Find, search for Email-to-Case.
3. Click Email-to-Case in the setup menu.
4. Confirm that the Insert Email Threading checkboxes for both Subject and Body are selected.
5. Click Save.

Step 2: Add Thread ID to Case Auto-Reply Email Templates

If you use Case auto-reply templates, the thread ID must be included in those templates.

1. Navigate to Setup > Classic Email Templates (or Email Templates).
2. Edit the email template used for Case auto-replies.
3. Set Field Type to Case Fields.
4. Select the field Case Thread ID.
5. Alternatively, type the merge field {!Case.Thread_Id} directly into the email template subject or body.
6. Save the template.

Step 3: Ensure the Reply-To Address Is the Email-to-Case Support Address

When replying to a customer from a Case, always change the From address to the Email-to-Case support address, not the Case owner's personal email.
If the reply is sent from the Case owner's personal email address, the customer's response is sent back to the owner's inbox and is not added to the Case thread in Salesforce.

Step 4: Add the Email Related List to the Case Page Layout

When a customer replies to an email containing the thread ID, Salesforce identifies the Case via the thread ID and adds the email to the Email related list on the Case.

1. Navigate to Setup > Object Manager > Case > Page Layouts.
2. Edit the Case page layout used by your support team.
3. Add the Emails related list to the layout.
4. Save the layout.

Step 5: Confirm Email Forwarding to Email Services Address

If you are testing Email-to-Case in a sandbox, or before deployment in production, confirm that the support email address has been forwarded (redirected) to the Email Services Address provided by Salesforce.
If this forwarding is not set up, customer replies are not reaching Salesforce and cannot be attached to the Case. Contact your Email Administrator to configure the forwarding rule.

Step 6: Check the Automated Case User Mailbox

If email forwarding is confirmed and replies are still not attaching, check the automated case user mailbox. The mailbox associated with the Automated Case User in Support Settings captures errors for any Email-to-Case processing failures.

1. Navigate to Setup > Support Settings.
2. Review the Automated Case User field.
3. Check the inbox of that user for bounced email notifications or error messages.

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