ServiceNow Learning 185: Why Inbound Email Does Not Trigger for External Users in ServiceNow CSM

[Shamma Negi]

Hi All,

When implementing email-based interactions in ServiceNow Customer Service Management (CSM), a common issue many developers and admins face is that the inbound email flow does not trigger for users who are outside your organization — meaning those who are not part of the ServiceNow "sys_user" table.

Let’s explore what’s happening behind the scenes, why this restriction exists, and how to handle it effectively.

How Inbound Email Processing Works in ServiceNow

ServiceNow processes incoming emails through a series of steps:

1. Email Received by the Email Server

   • Emails sent to a configured address (e.g., support@company.com) reach ServiceNow via SMTP.

   • ServiceNow polls the email server and retrieves the email.

2. Email Parsing

   • ServiceNow parses key parts: From address, Subject, Body, Attachments.

3. User Match

   • ServiceNow tries to match the sender’s email address to a record in the User (sys_user) table.

4. Inbound Actions / Email Rules

   • If user matching succeeds, email is processed by Inbound Email Actions.

   • In CSM, there are specialized flows such as Create/Reply to Case using Flow Designer or legacy inbound actions.

5. Record Creation / Updates

   • Based on the configured rules, ServiceNow creates or updates records (e.g., Cases, Tasks).

❗Why Inbound Email Doesn’t Trigger for External Users

At the core of the behavior I have observed is this: By default, ServiceNow only processes inbound emails if the sender is recognized as a user in the "sys_user" table.

This means:

✔️ If the sender’s email matches a ServiceNow user record → inbound email processing triggers normally.
❌ If the sender’s email address is not in "sys_user" → inbound email processing is skipped or treated differently.

stay tuned!

I will cover what fix can be done to allow this in ServiceNow in the next Blog.

Thanks,

Shamma Negi

ServiceNow CTA