This article outlines the database structure for the MMv4 em_queue database table.

• id
  Primary key of the em_queue table.
  int(10) | unsigned | auto increment | primary key| indexed
  
• cid
  System ID of the customer whom will receive this email.
  int(10) | unsigned | indexed
• email
  The email address in which the email will be sent to.
  varchar(255) | indexed
• batch_id
  System ID of the batch in which this email is associated with and will be sent with.
  int(10) | unsigned | indexed
• template_id
  System ID of the email template this email will be using.
  int(10) | unsigned | indexed
• series_step_id
  System ID of the email email series step this email will be associated with.
  int(10) | unsigned | indexed
• create_date
  The date in which the email was added to the Modular Mailer email queue.
  int(10) | unsigned | indexed
• send_date
  The date in which the email is to be sent.
  int(10) | unsigned | indexed
• hold
  The hold status of this email.
  int(10) | unsigned | indexed | 0/timestamp