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Error 'HTML File Upload Not Allowed' When Email-to-Case Email Contains an HTML File Attachment

Julkaisupäivä: Jun 2, 2026
Kuvaus

Overview

When an email is sent to an Email-to-Case or email service address, and that email contains an HTML file attachment, Salesforce rejects the email and does not create a case. The automated case user receives an error email with the following message:

HTML_FILE_UPLOAD_NOT_ALLOWED: Your organization has disabled uploads of this file type.

This error occurs because the org's File Handling Options are configured to block HTML file uploads as attachments or document records.

Ratkaisu

Root Cause

This error is triggered when the File Upload and Download Security settings in Salesforce are configured to "Don't allow HTML uploads as attachments or document records." HTML file attachments in incoming emails are subject to these org-level security settings.

How to Resolve the Error

To allow HTML file attachments to be processed by Email-to-Case, update the File Upload and Download Security settings:

  1. Go to Setup.
  2. In the Quick Find box, search for File Upload and Download Security.
  3. Click Edit.
  4. Locate the setting for HTML files.
  5. Change the setting from "Don't allow" to your organization's preferred option (for example, "Execute in sandbox" or "Allow").
  6. Click Save.

After saving, emails with HTML file attachments will no longer be rejected by Email-to-Case.
Note: Review your organization's security policies before changing this setting. Allowing HTML uploads may introduce security risks if the HTML files come from untrusted senders. See Configure File Upload  and Download Security Settings. 

 

Knowledge-artikkelin numero

000386561

 
Ladataan
Salesforce Help | Article