An Umbrella List is a mailing list whose subscriber base includes other mailing lists. It is usually used so that one email sent to a master (umbrella) list is automatically sent out to members of multiple sub-lists.

If your subscribers are likely to be subscribed to multiple sub-lists, then umbrella lists should be avoided if possible as subscribers will receive multiple copies of a single message. If your subscribers will not be subscribed to multiple sub-lists, then using a conventional umbrella list may be a good option.

• Some listservers (including Mailman) prepend multiple list names and signature lines in the final message. These can be disabled at the list administrator's discretion.
• When a list administrator needs to approve a posting to an umbrella list, they also have to approve the posting for each sub-list.
• Where archives are kept, messages posted to umbrella lists are archived in multiple locations.
• Mail loops may be created due to external mail alias configuration beyond the control of the list administrator.
• Umbrella lists may forward password reminders to the lists subscribed to the Umbrella list. If you are creating an umbrella list you may want to turn off password reminders. If reminders are to be sent, you will want to send password reminders and other administrative emails to -owner address instead of directly to users. Follow these instructions to configure your umbrella list to send administrative emails to -owner:
  
  1. Access the list administration website for your mailing list.
  2. Click General Options.
  3. Select Yes in the section labeled Send password reminders to, eg, -owner address instead of directly to user the default value is No).
  4. Selecting Yes in the above step will cause the option Suffix for use when this list is an umbrella for other lists, according to setting of previous umbrella_list setting to be applied. The default value is "-owner". This value should not be changed.