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Existing systems in use at SLAC and similar institutes
Send e-mail to random list of people
Mailing lists
majordomo system has been installed and in use at SLAC for some time.
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People often refrain from using mailing lists because of the fear of "spamming" people not interested in a specific topic and instead just send e-mail to a random list of people.
Hypernews
Hypernews has been used extensively by Babar, and is now also used by Geant4, CMS and LSST.
http://hypernews.slac.stanford.edu/
It is very popular with users, especially the threaded discussions, ability for users to browse existing discussions and opt-in to those that interest them and the ability to receive and respond to messages either via the web or e-mail. The implementation of hypernews is somewhat old and no longer being actively developed.
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