Duplicate messages

On a discussion list, people will sometimes send the same message several times to a mailing list.

Also, people will sometimes put an automated program on their email address, which answers each message it receives with a standard document. If that document should make it through to the mailing list, the second time that document is posted, ListManager will detect it as a duplicate posting because it is identical to the previously sent message.

This is known as a "duplicate message posting", and by default, ListManager is set to reject duplicate postings within a 2 day time period.

ListManager checks the first 200 characters of a message (about 3 lines) to see if it is a duplicate. The reason for checking only the first 200 characters is because some automatic response programs quote the previous message when they respond. Thus, causing each automatic response message to look "unique". If the entire message were used (as some list managers do), instead of the first 200 characters, then a mail loop could occur.

Note: Duplicate messages are counted on a per-member basis: if two different people send the same message, it is not seen as a duplicate.

See Utilities: List Settings: Discussion Group Features: Message Rejection Rules: Same Message Rules.