365 now allows an outbound gateway for entrusted mail. In order to begin using the EntrustedMail e-mail encryption services for Office 365, you must configure Office 365 to send outbound e-mail though the EntrustedMail encryption gateway. Once configured, EntrustedMail will inspect each message to determine whether to encrypt the message based on your organizational encryption policies.
For the full article link from 365, please see https://entrustedmail.com/support-overview/o365-outbound-gateway-setup
1. Set your browser to https://login.microsoftonline.com/.
2. Enter your admin email and password. (If you are not an admin, you will be pointed to the user page. You will need to contact your Office 365 Administrator for the required admin access).
3. Sign in and view the console.