Soapbox Mailer aims to have the smallest data footprint possible within Salesforce, saving you 50% on storage versus any other tool like it. To do this, we leverage existing objects in Salesforce when creating and sending and tracking messages. Here's an overview of what's being used.
Campaigns - the object that holds the email to be sent
Campaign Members - the object that holds the recipient information for one campaign (i.e. the Contact/Lead relationship, opens, clicks, bounces, complaints, etc)
Email Templates - the object that holds the HTML for the email templates you create
That's it! Now, since Soapbox Mailer is using standard Salesforce functionality, you'll find related data in other objects as well. For instance...
Contacts - the object's page layout can show Campaigns, which show all the email campaigns related to a Contact
Leads - the object's page layout can show Campaigns, which show all the email campaigns related to a Lead