Utilities: List Settings: Discussion Group Features: Message Rejection Rules: Same Message Rules
NOTE Identical messages sent to multiple segments or lists by the administrator through the administrative web interface are always allowed. However, members will only receive one copy of the message if Cross-Postings and Duplicates is set to "Make Sure That Multiple Copies of Cross-postings Are Removed."
Allow Duplicate Postings
A duplicate posting occurs when one person attempts to post a seemingly identical message to the same mailing list or segment more than once in one day.
ListManager looks at the entire message body to determine if a posting appears to be a duplicate.
Note that if duplicate postings are sent in multipart-alternative format, the content of the message may be the same but the boundaries may differ, causing a seemingly duplicate posting to be sent.
Normally, duplicate postings are the result of the author not being careful and sending the same message twice, or of some Internet mail error where the same message is delivered twice.
By default, ListManager rejects duplicate postings to all lists and segments via email.
NOTE This setting only applies to messages received via email or posted through the discussion forum interface. Duplicate postings by an administrator through the web interface are always allowed.
Normally you will want to leave this default setting as it is since there usually is no good reason why your list members would want to receive the same message twice. Also, this feature is quite effective as a mail-loop prevention technique, when people attach a misbehaving "automatic email answering" program to their email address.
Allow Cross-Posting?
This setting determines if messages that are cross-posted are rejected by ListManager or if they are allowed onto the list.
A cross-posted message is a single message sent to more than one mailing list or segment on a server. For example, in the To: field of an email message, the author can list several mailing lists and thus deliver the same message to several lists.
NOTE Messages will be compared with others posted to the list in the past 24 hours. Older postings will not be considered.
By default, email marketing and announcement will allow cross-posting, but discussion lists will not. If Allow Cross-posting? is set to No, ListManager will catch a cross-posted message, see that it has already been posted to another list and reject any further attempts to post the identical message. If the message is modified slightly in some way (i.e., an extra space, a carriage return, an extra sentence, etc.) it will not be considered a cross-posting. Note that Archives must be kept for at least one day for cross-posted messages to be removed.
In general, cross-posting to mailing lists is considered bad Internet etiquette and, occasionally, it is a method used by spammers to disseminate inappropriate email. However, there are many circumstances where it is appropriate. For instance, if there are two mailing lists or segments that deal with related topics, and messages appropriate to both groups are written, the author may want the message to be distributed to both mailing lists.
NOTE This setting only applies to messages received via email or posted through the discussion forum interface. Cross-posting is always allowed by the administrator through the administrative web interface.
Cross-Postings and Duplicates
If cross-posting is allowed, this setting determines what members of multiple lists or subsets will receive. Note that Archives must be kept for at least one day for cross-posted duplicates to be removed.
By default, members will not receive duplicate cross-posted messages.
For example, if a message is posted to two lists or segments and one person (one email address) is a member of both those lists or segments, the person will receive one copy of the posting, because the setting is "Make Sure that Multiple Copies of Cross-Postings are Removed."
However, there may be situations where you would like people to receive copies as posted to the lists or segments. If that is the case, change this setting to "Cross-Posted Copies Should be Sent to Recipients as Listed."
An example will help clarify how this feature works. Say you have several announcement lists where you post articles about various topics. You have lists named "computers", "cooking", "gardening" and "sports". People join the various lists that they are interested in. Some people join just one list, while others might join several lists.
Now, say that you have an announcement about a "video game for playing soccer" and you feel that it is appropriate for both the "computers" list and the "sports" list.
If you post your message to both "sports" and "computers" (i.e., you are "cross-posting" your announcement) people who are members of these two groups will receive your announcement.
If you are set to "Cross-Posted Copies Should be Sent to Recipients as Listed", then someone who is a member of both "sports" and "computers" will receive two copies of your message, one from each mailing list.
If you are set to "Make Sure That Multiple Copies of Cross-postings Are Removed", then someone who is a member of both "sports" and "computers" will only receive one copy of your message. They will receive the message from the first group you sent the message to. Thus, if you posted your message To: "soccer, computers" then the "soccer" messages are distributed first and that is where the person will get their message from.
This feature is particularly useful with announcement lists where you want to split your lists into various topics, but you have messages that apply to several topics. With other list managers, people would receive multiple copies. With ListManager, the duplicate messages are removed and people receive only one copy.
This feature works the same way when sending to multiple segments. For example, let's say you'd like to make an announcement to all administrators on your server. When selecting recipients for a mailing, you may select the administrators segment for each list. If your lists are set to "Make Sure That Multiple Copies of Cross-postings Are Removed", your administrators will receive only one announcement, regardless of how many lists they are members of.
More
1. Utilities: List Settings: Discussion Group Features
1. Utilities: List Settings: Discussion Group Features: Message Look
2. Utilities: List Settings: Discussion Group Features: Security
3. Utilities: List Settings: Discussion Group Features: Message Rejection Rules
1. Utilities: List Settings: Discussion Group Features: Message Rejection Rules: Blanks
2. Utilities: List Settings: Discussion Group Features: Message Rejection Rules: Same Message Rules
3. Utilities: List Settings: Discussion Group Features: Message Rejection Rules: Etiquette