Use of the mailing lists is covered under the Terms of Service in the LegalNotice for this system.

Messages from addresses not subscribed to the list are silently dropped by the mail system (this is due to the weight of spam on today's Internet).

Most of the lists are not moderated; any subscriber can post. The exception would be the AnnounceList. Most subscribers are flagged for moderation, so if they attempt to post, their mail is held until a list admin can release it.

Each list's info web page (provided by GNU Mailman) details the topic/charter of the list. Abuse is dealt with manually, and generally after-the-fact.

There is on-going discussion about how we should best address the question of "topic" and "acceptable messages" to the gnhlug-discuss list.