A guest post from my cohort on the Office content publishing team:
Forefront Online Protection for Exchange (FOPE) users commonly ask about creating a footer for outgoing email. You may want to add a disclaimer to your outbound email for HIPAA or other legal compliance reasons, or you may simply want to add your organization’s logo or contact information to all outgoing email. Whether you are a FOPE standalone, Office 365 for enterprises, or Live@edu customer who wants to create an email footer, we’ve got you covered. Create an E-mail Footer for Outbound E-mail on TechNet details the steps involved for creating a footer for all of your outbound email, using tools available in the FOPE Administration Center.
If you are an Office 365 for professionals and small business customer, you can create a signature in Outlook for all outgoing mail. To learn how you can automatically include signatures in Outlook and Outlook Web App for Office 365, read the E-mail Signature topic on help.outlook.com.
One final word: On the Forefront Online Protection for Exchange (FOPE) FAQ in the Office 365 community we recently added a question and answer about email footers. You can also find additional questions and answers about FOPE that you may be looking for.
I hope this helps.
Timothy Rich, Forefront User Assistance