I've tried multiple things, but I can't seem to add Case Comments to my cases through Email-to-case. At the moment I have done the following:

  • Enabled email-to-case and added a routing address in order to get an Email Services Address
  • Created the Thread_Id__c custom field in the Case standard object with the formula provided by Salesforce here.

Now, what I do to try to add case comments is:

  1. Create a case with a Contact which has my email and other required information.
  2. Send an email to the Email Services Address with the case's thread Id both in subject and body.

The result is that a new case is created instead of a comment being added to the existing case whose Thread Id I have copied in the email.

Do any of you know what I'm missing?

1 Answer 1


You should be using {!Case.Thread_Id} in your email templates. The formula in the link you provided was not provided by salesforce.com, but just a random customer that felt they wanted to demonstrate how their formula was (which is incorrect). It's been revealed that the fifth character of an ID is actually part of the pod Id, which was only recently incremented from 0. You could modify the formula to take the left 5 characters, and the remainder would be approximately correct, but using the merge field would be a better choice.

  • I tried to create a template in which the main object is the case, so I tried to use {!relatedTo.Thread_Id} but I get the "field does not exist for object Case" error. Is this field valid? How can this be enabled? Commented Oct 5, 2017 at 17:46

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