How to Apply Sensitivity Labels to Outlook Email With Microsoft Purview

Sensitivity labels from Microsoft Purview let you classify and protect email content directly in Outlook. These labels apply encryption, watermarking, and header markings to prevent data leaks. You might need to apply a label because your organization requires it for compliance or because you want to control who can read or forward an email. This article explains how to apply sensitivity labels in Outlook for Windows, Outlook on the web, and Outlook for Mac. You will learn the steps to manually label email, set default labels, and understand what happens after a label is applied.

Understanding Sensitivity Labels and Prerequisites

Sensitivity labels are part of Microsoft Purview Information Protection. They allow organizations to classify data based on sensitivity levels such as Public, Internal, Confidential, and Highly Confidential. Each label can enforce protection actions like encryption, access restrictions, and visual markings such as headers or footers. Before you can use sensitivity labels in Outlook, your IT administrator must publish the labels from the Microsoft Purview compliance portal. The labels must be configured in the Label policies section and assigned to users or groups. You also need a Microsoft 365 subscription that includes Microsoft Purview, such as Microsoft 365 E3 or E5, or a standalone Information Protection plan. Outlook for Windows version 2104 or later, Outlook on the web, and Outlook for Mac support sensitivity labels natively. If you do not see the Sensitivity button in Outlook, contact your administrator to confirm the policy is assigned to your account.

Steps to Apply a Sensitivity Label in Outlook for Windows

The Sensitivity button appears in the Home tab of the ribbon when composing a new email. Follow these steps to apply a label.

1. Open a new email message
   In Outlook for Windows, click New Email on the Home tab. The compose window opens with the ribbon available.
2. Locate the Sensitivity button
   On the ribbon, find the Sensitivity button in the Tags group. If you do not see it, click the three-dot overflow menu to expand the ribbon.
3. Select a sensitivity label
   Click the Sensitivity button. A dropdown list shows all labels published to your account. Click the label you want, such as Confidential. The label name appears next to the Sensitivity button, and the email subject line may show a colored bar or marking depending on the label configuration.
4. Verify the label is applied
   Look at the top of the email compose window. The Sensitivity button now displays the selected label name. If the label includes encryption, a lock icon appears in the To field area. You can also click the Sensitivity button again to change or remove the label.
5. Send the email
   Complete your email and click Send. The label and its protection settings travel with the message. Recipients see the label marking and must meet the access requirements to read the email.

Steps to Apply a Sensitivity Label in Outlook on the Web

Outlook on the web offers the same labeling capability through the compose toolbar. The process is slightly different from the desktop version.

1. Start a new message
   In Outlook on the web, click New message in the top-left corner. The compose pane opens on the right side of the screen.
2. Open the More actions menu
   In the compose toolbar, click the three-dot icon labeled More actions. A dropdown menu appears.
3. Select Set sensitivity
   From the menu, click Set sensitivity. A list of available labels appears. Click the label you want to apply, such as Internal. The label name appears at the top of the compose pane.
4. Check the label indicator
   A colored banner may appear at the top of the email to indicate the sensitivity level. If the label requires encryption, you will see a lock icon next to the recipients.
5. Send the email
   Fill in the recipient, subject, and body. Click Send. The label is applied to the outgoing message.

Setting a Default Sensitivity Label for All New Emails

Your administrator can enforce a default label for all new emails. If a default label is not enforced, you can set one manually in Outlook options. This ensures every new email starts with the correct classification.

1. Open Outlook Options
   In Outlook for Windows, click File in the top-left corner. Then click Options at the bottom of the left pane.
2. Go to Mail settings
   In the Outlook Options dialog, click Mail in the left sidebar. Scroll down to the Compose messages section.
3. Set the default sensitivity label
   Under Default sensitivity label, click the dropdown and select the label you want as the default. For example, select Internal if most of your emails are internal communications.
4. Save the setting
   Click OK at the bottom of the dialog. All new emails you compose will now start with the selected label. You can still change the label for individual messages using the Sensitivity button.

Common Issues When Applying Sensitivity Labels

The Sensitivity button is missing in Outlook

If you do not see the Sensitivity button in the ribbon, the label policy may not be assigned to your account. Contact your IT administrator to confirm your account is included in the label policy. Also verify that your Outlook version is up to date. For Outlook for Windows, go to File > Office Account > Update Options > Update Now to install the latest updates.

A label cannot be applied to an existing email

Sensitivity labels apply only to new, reply, or forwarded messages. You cannot apply a label to an email that has already been sent. To label a sent email, you must forward it or create a new message that includes the original content.

The default label does not appear on new emails

If your administrator has set a mandatory default label, your manual setting in Outlook Options may be overridden. Check the label policy in the Microsoft Purview compliance portal. If the policy enforces a default label, Outlook will use that label regardless of your personal setting. You can still change the label for individual messages unless the policy restricts changes.

Manual Label vs Default Label vs Mandatory Label: Key Differences

Item	Manual Label	Default Label	Mandatory Label
Who sets it	User selects from Sensitivity button	User sets in Outlook Options or admin sets in policy	Admin enforces via label policy in Purview
When applied	Per email at compose time	Automatically on every new email	Automatically on every new email; cannot be removed
User can change	Yes, before sending	Yes, before sending	No, unless policy allows downgrade
Use case	Ad-hoc classification for sensitive threads	Consistent baseline for all internal emails	Regulatory compliance where all email must be labeled

Understanding these three modes helps you choose the right approach for your workflow. Manual labels give you full control. Default labels save time. Mandatory labels ensure no email leaves without a classification.

You can now apply sensitivity labels in Outlook for Windows, Outlook on the web, and Outlook for Mac. Set a default label to automate classification for routine emails. If you work with highly sensitive data, explore the Purview compliance portal to create custom labels with encryption and watermark settings. For advanced protection, combine sensitivity labels with Microsoft Purview Data Loss Prevention policies to block emails that contain credit card numbers or other sensitive information.