With Office 365 Message Encryption, your organization can send and receive encrypted email messages between people inside and outside your organization. Office 365 Message Encryption works with Outlook.com, Yahoo!, Gmail, and other email services. Email message encryption helps ensure that only intended recipients can view message content.

How Office 365 Message Encryption works

Office 365 Message Encryption is an online service that's built on Microsoft Azure Rights Management (Azure RMS) which is part of Azure Information Protection. Office 365 administrators can define mail flow rules to determine the conditions for encryption. For example, a rule can require the encryption of all messages addressed to a specific recipient.

When someone sends an email message in Exchange Online that matches an encryption mail flow rule, the message is encrypted before it's sent. All Office 365 end-users that use Outlook clients to read mail receive native, first-class reading experiences for encrypted and rights-protected mail even if they're not in the same organization as the sender. Supported Outlook clients include Outlook desktop, Outlook Mac, Outlook mobile on iOS and Android, and Outlook Web App.

Recipients of encrypted messages who receive encrypted or rights-protected mail sent to their Outlook.com, Gmail, and Yahoo accounts can easily authenticate to the OME portal using their Microsoft account, or Gmail or Yahoo credentials.

End-users that read encrypted or rights-protected mail on clients other than Outlook also use the OME portal to view encrypted and rights-protected messages that they receive.

We've increased the size limits for messages and attachments that you can encrypt using Office 365 Message Encryption. For more information about limits, see Exchange Online Limits.

Defining rules for Office 365 Message Encryption

One way to enable the new capabilities for Office 365 Message Encryption is for Exchange Online and Exchange Online Protection administrators to define mail flow rules. These rules determine under what conditions email messages should be encrypted. When an encryption action is set for a rule, any messages that match the rule conditions are encrypted before they're sent.

Mail flow rules are flexible, letting you combine conditions so you can meet specific security requirements in a single rule. For example, you can create a rule to encrypt all messages that contain specified keywords and are addressed to external recipients. The new capabilities for Office 365 Message Encryption also encrypt replies from recipients of encrypted email.

For more information about how to create mail flow rules to take advantage of the new OME capabilities, see Define Rules for Office 365 Message Encryption.

Sending, viewing, and replying to encrypted email messages

With Office 365 Message Encryption, users can send encrypted email from Outlook and Outlook on the web. Additionally, admins can set up mail flow rules in Office 365 to automatically encrypt emails based on keyword matching or other conditions.

Recipients of encrypted messages who are in Office 365 organizations will be able to read those messages seamlessly in any version Outlook, including Outlook for PC, Outlook for Mac, Outlook on the web, Outlook for iOS, and Outlook for Android. Users that receive encrypted messages on other email clients can view the messages in the OME portal.