Many emails that leave your organization should have a footer with some legal jargon on them.

I'll show you how to add a rule that will stamp all outbound email with a footer.

  1. Log into your Office365 Admin portal.
  2. Locate the "Exchange" menu item under "Admin Center" and click on it.  This will open the Exchange Admin Center in a new tab or window.
  3. Locate, on the left hand side, the menu item "Mail Flow" and click on it.
  4. Under "Rules" click on the [+] to add a rule.
  5. Name the rule something like "Domain Email Footer".
  6. Click on the drop down under "Apply this rule if..." and pick "The recipient is located..." from the list.
  7. Pick "Outside the organization" from the options window.
  8. Click on the drop down under "Do the following..." and pick "Append the disclaimer..." from the list.  Click OK.
  9. You will need to enter some disclaimer text into the "specify disclaimer text" window.  It CAN be HTML.  Click OK.
  10. Under "Properties of this rule:" enter the correct priority.  It does not need to be first.
  11. Under "Choose a mode for this rule:" pick "Enforce".
  12. Click "Save"

You just added a rule to add a disclaimer.

Now, go and test it with your GMail account to make sure it looks right.

Hope this helps.