Shotgun email refers to an email requesting information or action that only requires the efforts of one person but is sent to multiple people in an effort to guarantee that at least one person will respond.
Shotgun emailing is considered poor internet etiquette.
[1] An example would be a person of authority in a business organization sending out an email to five technicians in the information technology department of his company to let them know his printer is broken.
One technician responds with an on-site call and fixes the problem.
Later in the day, other technicians follow-up to fix the printer that is already back in order.