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In an ideal world people would only send messages to a mailing list in order to communicate useful information to people on that mailing list. Unfortunately in the real world people have an unpleasant habit of posting unwanted messages to mailing lists. This normally happens when people reply to a message and copy their response to the list by accident. However there has been an unpleasant and increasing trend for people to send unsolicited junk email to mailing lists in order to promote some product or event. This can be extremely disruptive with large mailing lists, especially when the list members do not understand why they are receiving these messages. To help combat this threat, several different types of mailing list exist, each type targeted at a different audience.

 

 

People who can send messages to the list

Anyone (apart from senders explicitly blocked or moderated)

Anyone, anywhere in the world can send a message to an open list. This clearly has high potential for abuse. It should only be used for widely published contact addresses, for example a list set up to handle undergraduate admissions queries would clearly need to be an open list. List managers should restrict list membership to a small number of responsible individuals who understand that junk mail can be sent to an open mailing list.

Anyone, but moderate messages scored as spam

As above, but external messages which the system has scored as spam are are sent to the list managers or moderators for further attention.

Anyone, but discard messages scored as spam

As above, but external messages which the system has scored as spam are discarded.

cam.ac.uk users, members, managers and moderators + allowed senders

(Previously known as "Opencam").

People with Cambridge email addresses (that is, an email address that ends in cam.ac.uk) can post to an Opencam list. So can the list managers, moderators (if the list manager has nominated any) and anyone on the authorised sender list. Messages from other (i.e. unauthorised) senders are sent to the list managers or moderators for further attention. This is a slightly more secure state than a straight open list. It is principally designed to stop unwanted junk email from being sent to the list by people outside Cambridge.

Each mailing list has a set of Blocked Senders, Moderated Senders and Allowed Senders which can be used for  fine grained control. All three start out empty.

cam.ac.uk users, members, managers and moderators. Discard other senders

As above, but any messages which do not come from a known good sender are discarded.

List members, moderators, managers + allowed senders. Otherwise Moderate

 (Previously known as "Closed").

Only list members, managers, authorised senders and any nominated list moderators can post messages to a closed list. This is the natural state for a small discussion list where a few dozen people want to communicate freely with each other, but don't want unwelcome interruptions from people outside the list.

Messages from unauthorised senders are forwarded to the list moderators. (If no moderators have been set up, the list managers automatically become moderators). A message is also sent back to the originator of the message to explain the situation.

The moderators can then approve or reject the message via the web interface (a link is included in the message they receive). Alternatively it is possible to approve posting by sending a message to sympa@lists.cam.ac.uk by following instructions in the moderation message.

Each mailing list has a set of Blocked Senders, Moderated Senders and Allowed Senders which can be used for  fine grained control. All three start out empty.

List members, moderators, managers + allowed senders. Discard other messages

As above, but any messages which do not come from a known good sender are discarded.

List moderators, managers + allowed senders. Moderate other messages

(Previously known as  "Restricted").

Only list managers/moderators and a nominated set of authorised senders are allowed to post messages. Any other messages sent to the list must be explicitly approved by one of the list moderators. (If no moderators have been set up, the list managers automatically become moderators). 

This is the natural state for very large mailing lists used for announcements (e.g. society mailing lists). Messages from unauthorised senders are forwarded to the list managers/moderators who can then take action as outlined in the section on "closed" lists above. A message is also sent back to the originator of the message to explain the situation.

Each mailing list has a set of Blocked Senders, Moderated Senders and Allowed Senders which can be used for  fine grained control. All three start out empty. 

List moderators, managers + allowed senders. Discard other messages

As above, but any messages which do not come from a known good sender are discarded. This might be suitable for an announcement list where only a small set of people ever need to send messages.

Moderation forced for ALL messages

(Previously known as  "Secure").

Every message sent to the list is forwarded to the list moderators even if the message appears to originate from a list manager or moderator in the first place. A second message may be sent back to the originator of the message to explain the situation. Note that the whitelist is ignored when the status is set to secure: all messages must be explicitly approved by a list moderator.

At face value there would seem to be no advantage in using a secure mailing list in preference to a normal moderated (restricted) list and substantially more work is involved for the list moderators. However, it is an unfortunate fact of life that it is very easy for people to forge email messages. If someone insists on trying to post messages to a closed or moderated (restricted) list by forging messages as a list moderator, the list manager can simply force moderation until the problem has been dealt with. This is preferable to shutting the list down entirely.

Blocked Senders can be used to silently reject messages. Allowed senders is not used: moderation is forced in all other cases.

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