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CSAIL standard configuration for a discussion list

One common use for a mailing list is for discussion among list members. In this case, typically, most or all of the list members are authorized to post to the list, and often postings to the list generate replies, also on the list.. (The other two use-cases we have preconfigured templates for are announcement lists and contact-point lists.) The CSAIL standard template for a discussion list specifies:
  • Maximum message size (max_message_size) of 40kB. (Since discussion lists often have large numbers of subscribers at any one site, it may not be safe to allow large messages, although 80kB is probably OK if appropriate for your list.)
  • The “List-Post:” header is included on messages (include_list_post_header); some mail clients will take this as a hint to provide a “Reply to list” or “Post to list” command.
  • Both automated confirmation (that the email address is valid and belongs to somebody who wants to subscribe to the list) and moderator approval are required for subscription (subscribe_policy). Some discussion lists allow anybody in the world to subscribe; if yours does, you’ll want to change this under “Privacy options...” > “Subscription rules”. (Of course, that can be problematic if anything remotely controversial is ever discussed on the list.)
  • When people subscribe to the list, they can immediately post to the list without moderator approval (default_member_moderation). (See below about changing this if you like.)
  • Any messages from nonmembers will be held for moderator approval (generic_nonmember_action). Such mail may be from people authorized to post to the list (in which case you might want to add their addresses to accept_these_nonmembers under “Privacy options...” > “Sender filters”), but it’s quite likely to be spam, so it’s not safe to allow through without moderator oversight. (And it’s also not safe to reject it, since spam often forges the sender address, and the rejection notices are likely to go to innocent bystanders.) If you’re sure the list is properly configured to allow mail through from all addresses that should be allowed to post, and legitimate posters are never going to accidentally post from the wrong address, you could change this to ”Discard”, though.
  • The list address has to be explicitly mentioned in the message headers (require_explicit_destination), i.e. in the To: or Cc: lines, or posts will be held for moderator approval. This helps avoid spam getting through, and also makes it clear to list recipients why they’re getting a message.
Of course, you can change any of these settings via the list administrator web interface at
The information page about the list, which you can point people at to subscribe themselves or learn more about it, is

Things you should adjust

In addition to getting subscribers on your list (either by announcing the list and letting them request to be added via the web interface, or by adding them manually through the “Membership Management...” > “Mass Subscription” page), you’ll want to:
  • You should add a paragraph or two of human-readable description about your page in the info field under “General Options”. This will be displayed on your list info page. If you explain the purpose of the list there in sufficient detail, this can also be tremendously useful for TIG years down the road when all the people authorized to manage a list have left CSAIL and we’re trying to figure out whether it’s still in use.
  • If you want to have all posts to the list require moderator approval, or if you want new members to need moderator approval for a little while so you can make sure they’re not spammers or malicious (or just that they understand your list’s purpose and social norms), you may want to turn on default_member_moderation under “Privacy options...” > “Sender filters” before anybody gets subscribed. You can then turn off individual list members’ moderation checkboxes under ”Membership Management...” on a case-by-case basis.
  • By default, CSAIL mailing lists are included in the list of mailing lists we host at . If you don’t want your list included there, you can turn off advertised under “Privacy options...” > “Subscription rules”. Anybody who knows or can guess the name of your list can still get to its own listinfo page with all the information, but leaving it off the main list will somewhat decrease the likelihood that people or bots will stumble across it accidentally.
  • If your list is archived, especially if it’s a very low-volume list, you may wish to adjust the “archive_volume_frequency” (essentially, what time period a single index page of list messages includes) under “Archiving options”. See also below.
  • And especially if this is the first list you’re administering you should really at least skim through all the configuration options so you get a sense for what you can configure. Feel free to contact us at for advice or if you have any questions.


Consider the content of your list when choosing whether the list archives are public (visible to anybody at all on the web) or private (visible only to the list members, or people who can guess their membership passwords). You can choose that when creating a list with the CSAIL list creation form but you can also adjust it after the fact. For instance, a list for announcements of new releases of Free or open-source software might reasonably have public archives, because you’d want people to be able to find that information on the web even if they weren’t subscribed to the list. Of course you have no control over list members sharing their passwords, so if your list is going to get any traffic that really shouldn't be found on the web you may wish to turn off archives altogether. (Then again, your list members can still share their email passwords — or have them guessed or stolen —, or manually forward list messages)

-- JaySekora - 07 Jan 2017
Topic revision: 08 Jan 2017, JaySekora

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