Insert custom email headers into an outbound email from the ServiceNow instanceUse a business rule to insert custom email headers into an outbound email generated from the default ServiceNow mail infrastructure instance. A business rule is a server-side script that runs when a record is displayed, inserted, updated, or deleted, or when a table is queried. For details on business rules and complete field definitions, see the product documentation, Classic business rules. Note: If your instance uses your organization's own mail server or a hosted service such as Office 365, set up a rule using your mail server software or service to add the custom header. Create the business rule Select or complete the following options: Name: Add Custom Email Headers (or a name of your choosing)When to run: Before Select InsertSelect Update Order: 100Advanced Use the following script as an example (replace X-MyCustomHeader with the name of the header and current.instance with the variable or literal value that you want in the header: (function executeRule(current, previous /*null when async*/) { if(current.headers.indexOf("X-MyCustomHeader") < 0){ current.headers = "X-MyCustomHeader:" + current.instance + "\n" + current.headers; }})(current, previous); Applicable versions This was tested on the Madrid release, but will most likely work on other versions. Additional information This solution is considered a customization and out of scope for support, and cannot be guaranteed to always work in a future version of ServiceNow. Credit for the business rule code above goes to several ServiceNow Community posts on this subject, and was also tested as working by a customer who raised a case on the issue.