Enable internal relay domain

Enabling internal relay will forward email sent to users that do not exist on the Office 365 server to the MX records of the domain.

Admin Portal

Admin Portal

Login to Admin Portal with admin account.

Exchange Admin

Exchange Admin

Click the Admin drop down menu in upper right and click Exchange.

Exchange admin center

  1. Click mail flow on the right.
  2. Click accepted domains from top menu.
  3. Double click on your domain.

Click the radial button for internal relay domain and click save.

This will forward email to users that do not exist on the Office 365 server to the MX records of the domain.