Prerequisite: Add custom add-in to monitor and block sent emails in new Outlook for macOS

This section explains how to add a custom add-in to monitor and block the sent emails on your macOS.

Install Trellix Data Loss Prevention
Make sure that the Python HTTPS web server named outlook_monitor is always running.
Set the self-signed certificate to Always Trust in the System Keychain using the Keychain Access application or by running the sudo security add-trusted-cert -d -r trustRoot -k /Library/Keychains/System.keychain /usr/local/McAfee/DlpAgent/bin/outlook_monitor.bundle/localhost.pem command in the command line interface.

For Admin-managed accounts, the custom add-in must be deployed using Microsoft Office 365 Admin Center or Microsoft Exchange Admin Center. You can learn more about deploying add-ins at Deploy add-ins in the Microsoft 365 admin center

Note
Admin managed accounts also require an XML manifest file, which can be found at /usr/local/McAfee/DlpAgent/bin/outlook_monitor.bundle/dist/manifest.xml

Custom add-ins are added to your account, not to macOS devices.

To add the custom add-in to your user-managed account:

In Microsoft Outlook, go to Menu → Tools → Get Add-ins.
On the left pane, click My add-ins → Custom add-ins → Add a custom add-in → Add from a file....
Browse to the file path /usr/local/McAfee/DlpAgent/bin/outlook_monitor.bundle/dist/manifest.xml and click Install.

The custom add-in monitors email headers, email bodies, and attachments for any sensitive content.

Note
To disable the custom add-in from monitoring sent emails for an admin-managed account, you must disable it from the Admin Center of Microsoft Office 365 Admin Center or Microsoft Exchange Admin Center.