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, Lyris List Manager 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, Lyris List Manager is set to reject duplicate postings within a 2 day time period.
Lyris List Manager 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.