To create a custom email template, navigate to Configurations >> Email Templates >> Add
Give the template an appropriate Name (For example: Upcoming Auctions). For Category select Custom Email. Fill in all other fields. Be sure to save it.
Note: You will be able to edit the body of the email each time you send out a new email using this template.
Once saved you can send a bulk email from the Contacts >> Email All. Be sure to select the name of the Email Template you created.