A single bulk email is a way to send one email to a group of people. You would use a bulk email to send out things like newsletter blasts, sales you might be offering, and for advertising things like mini sessions.
To create a new bulk email:
Go to the Email Marketing page.
Click the "Add New" button.
Click "Single Bulk Email" in the dropdown.
While editing a single bulk email, there are 3 sections:
Auto-add settings, which is how you configure who (in your Sprout account) will receive this email. You can build a set of filters for your contacts, leads, shoots, galleries, and gallery guests.
Email list, which will preview a list of recipients based on your auto-add settings. You can also manually add new contacts, and existing contacts or import a CSV of contacts from here.
Email, which is where you'll edit the email to be sent.