Mail security isn't set up correctly for the domain '{0}'. To fix it, you'll need to contact the owner of '{0}' because that ...

Mail security isn't set up correctly for the domain '{0}'. To fix it, you'll need to contact the owner of '{0}' because that domain isn't part of your Office 365 environment. They might need to update their SPF record at their DNS host provider. For information that could help them, click the 'Get help fixing this issue' link on the right side of the screen.