When you set up an email blast using the mass email wizard, you use the WYSIWYG editor to enter the content/images/etc. for the email blast.
When the email blast is sent, additional text is added in the footer of the message (this text is not visible anywhere in 360 or in the preview emails).
There are 2 values in that footer that are controlled by settings in 360. If those settings are not populated in 360, then the corresponding content will not be populated in the footer. To get to this mouse over Settings > Click on Account Settings
See the screenshots below: