If you are using the Firecart editor to create your HTML email, the editor will automatically insert your address details so that the email follows anti-SPAM best practices.
The footer of the email is automatically created based on the business details that have been setup on your Firecart account.
Hence, if you want to make any changes to the footer, they will be a byproduct of changes made to your business details.
View the following two screenshots of the "Edit Business Details" page and the footer of the email.
Edit Business Details Screenshot
Footer of the email
Any change made to the Business Details section, will reflect in the footer of the emails being sent out to your customers.
In cases, where you want complete control over how the email looks, we recommend using the upload HTML feature on Firecart.