List Flag: ticketed

Sets the list to be ticketed.  A "ticketed" list is one in which mnemonics
are used to identify common threads.  When this flag is on, the Subject:
line has a mnemonic added only if none is already present.  Moreover, the
sequence number of the list is not increased unless a mnemonic is added.

This flag has no meaning unless the "mnemonic" flag is also set.

See also: mnemonic