People sometimes post personal information of various kinds, often in 'signatures' only to discover that the list has a public archive and this info is now indexed in search engines. They then want the info removed from the web. This is at best, a time consuming job for the Mailman site admin to do it right.
It would be nice if there was a way to prevent this from occurring in the first place.
It has been suggested that the first time a user posts to a list with public archives, the post be held and the user be sent a message explaining that the post will be publicly archived, and the user be given the option of confirming or cancelling the post. Such a feature is not available in current Mailman, but there is a way to partially accomplish it anyway.
Here are the steps needed to do this.
Set the list's General Options -> respond_to_post_requests to Yes so that the poster of a held message is notified.
Set the list's Privacy options... -> Sender filters -> generic_nonmember_action as desired, but other than Accept so a nonmember post can't go to the list without being held.
Set the list's Privacy options... -> Sender filters -> default_member_moderation to Yes so new subscribers are moderated by default
These steps will ensure that a first post will be held for moderator approval before going to the list and archive and that the poster will be sent a notice. The final step is to create a list specific version of the postheld.txt template. Currently, this require site admin action as described at 4.48 How can I change the HTML (or .txt) templates used by my mailing lists?, but beginning with Mailman 2.1.23, a list admin will be able to edit this via the web admin "Edit the public HTML pages and text files" function.
The default postheld.text template says at the bottom
Either the message will get posted to the list, or you will receive notification of the moderator's decision. If you would like to cancel this posting, please visit the following URL: %(confirmurl)s
You may wish to change other parts of this template, but at a minimum, you would change this last part to something like
Please note that if this post is accepted for the list, it will be stored in a public archive and any personal information in the post or a signature will be available and searchable on the world wide web. If this is not acceptable, go to %(confirmurl)s and cancel this post *NOW* before a moderator approves it.
Then you would also not be too quick to accept moderated posts to give the user time to receive and read the notice.