Penn Computing
Computing Menu Computing A-Z
Computing Home Information Systems & Computing Penn

Reflector Lists


When you need to send mail to a group of people and other people need to send mail to that same group of people, a reflector list or system alias may be the best vehicle.

A reflector list is an mail address known to your mail system which is a substitute for a list of other mail addresses. For example, "" may be a substitute for
When you send mail to "", your mail message goes to the above mail addresses and your mail header only contains the name of the reflector list, "", not the individual mail addresses within the reflector list.

Since a reflector list is a real system email address, anyone who knows this mail address can use the reflector list to send mail to the addresses within the list. The addresses within a reflector list are usually contained in a file. You can somewhat control mailings to a reflector list by changing the permissions on that file although this kind of administration may become cumbersome. When lists that are being used to make announcements, consider sending the message to yourself and blind-copying the list. This will prevent unwanted mail from going to all members of the list.

You will need to check with your email provider to see if you are allowed to create reflector lists and to get details on the procedure.

Managing the Reflector List

  1. It is the list owner's responsibility to manage their own reflector list, adding or deleting members.
  2. Before creating a reflector list, list members should know that they are being added to a reflector list or the proper University authorization must be obtained.
  3. The list owner should provide and announce the mechanism that will allow members to unsubscribe themselves from the list. For a reflector list, members can usually unsubscribe themselves by sending mail to
    where "listname" is the name of the reflector list and "host" is the name of the mail server. List members should not send mail back to the list asking to be removed from the list.
  4. The list owner should avoid overloading computing resources. The list membership should be of a reasonable size. If you need to send information to a large number of people, please consider other means:
  5. Use Bcc: If you are using your reflector list to make announcements and there is no reason for the members to respond to the entire list, you can avoid any unnecessary mailings to the entire list by sending the message to yourself and blind copying the reflector list.
    From: John Doe <>
    Subject: Meeting
    By blind copying your list, any responses to the message will only be sent to you and not to the entire list. For large reflector lists, we strongly recommend blind copying the reflector list for all mailings.

Information Systems and Computing
University of Pennsylvania
Comments & Questions

University of Pennsylvania Penn Computing University of Pennsylvania Information Systems & Computing (ISC)
Information Systems and Computing, University of Pennsylvania