---
description: Blocked content rules in Email Security.
title: Blocked content
image: https://developers.cloudflare.com/og-docs.png
---

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# Blocked content

Last updated Aug 24, 2026|Copy as Markdown|[View as Markdown](https://docs-durable-objects-instance-replaced-errors.previews.developers.cloudflare.com/cloudflare-one/email-security/settings/detection-settings/blocked-content/index.md)|[Agent setup](https://docs-durable-objects-instance-replaced-errors.previews.developers.cloudflare.com/agent-setup/)

Email security allows you to configure blocked content rules that match against the content of incoming messages. When a message matches a rule, Email security marks it with a malicious [disposition](https://docs-durable-objects-instance-replaced-errors.previews.developers.cloudflare.com/cloudflare-one/email-security/reference/dispositions-and-attributes/), preventing it from reaching users' inboxes.

Blocked content rules are available for the **Enterprise** and **Enterprise + PhishGuard** Email security packages.

## How blocked content works

Blocked content rules let you define your own content-based blocking criteria. Each rule specifies a pattern — either a plaintext string or a regular expression — and the part of the message that Email security should scan for it.

You can scan the following fields:

* **Subject**: Match the pattern against the message subject line.
* **Body**: Match the pattern against the message body.
* **Subject and body**: Match the pattern against both the subject and the body.

If the pattern matches, Email security marks the message as malicious. Blocked content rules only support the block action.

### Example of a blocked content rule

Your organization is being targeted by a phishing campaign that uses subject lines containing variations of `Urgent: Payroll Update Required`. You can create a blocked content rule with the regular expression `(?i)urgent.*payroll.*update` scanning the **Subject** field to block any message that matches this pattern.

## Configure a blocked content rule

To create a blocked content rule:

1. Log in to [Cloudflare One ↗](https://one.dash.cloudflare.com/).
2. Select **Email security**.
3. Go to **Policies & rules** \> **Blocked content**.
4. Select **Add a rule**.
5. Enter the rule information:  
  * **Name**: A descriptive name for the rule.
  * **Match type**: Choose between:  
    * **Plaintext**: Email security matches the exact string you enter.
    * **Regular expression**: Email security evaluates the pattern as a regular expression. Regular expressions must be valid Java expressions.
  * **Pattern**: The plaintext string or regular expression to match against.
  * **Search location**: Choose which parts of the message to scan:  
    * **Subject**
    * **Body**
    * **Subject and body**
  * **Notes** (optional): Provide additional information about the rule.
6. (Optional) Use the built-in **Regular expression checker** to validate your pattern before saving. The checker lets you test your pattern against sample text to confirm it matches as expected.
7. Select **Save**.

## Validate a regular expression

When you choose **Regular expression** as the match type, Email security provides a regular expression checker to help you validate your pattern before saving the rule.

To validate a regular expression:

1. On the **Add a rule** page, select **Regular expression** as the match type.
2. Enter your regular expression in the **Pattern** field.
3. In the **Test your expression** field, enter sample text that represents the content you want to match.
4. Email security displays whether the sample text matches your pattern.
5. Adjust the pattern as needed and repeat until it behaves as expected.

Cloudflare recommends validating every regular expression before saving to avoid false positives and false negatives.

## Edit a blocked content rule

To edit a blocked content rule:

1. On the **Blocked content** page, select the rule you want to edit.
2. Select the three dots > **Edit**.
3. Edit the rule.
4. Select **Save**.

## Delete a blocked content rule

To delete a blocked content rule:

1. On the **Blocked content** page, select the rule you want to delete.
2. Select the three dots > **Delete**.
3. On the pop-up message, select **Delete**.

To delete multiple blocked content rules at once:

1. On the **Blocked content** page, select the rules you want to delete.
2. Select **Action**.
3. Select **Delete**.

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