List flag: redirect

Causes the "domain" field to be interpreted as the new home of the specified
list.  Instead of creating aliases on the local machine that indicate a
locally-operated list, lists with this flag set and a non-empty "domain" field
will cause aliases to be created that forward list-related traffic to the
list at the specified "domain" instead.

For example, if you operate a list called "foobar" based at "hookup.net",
and you set the "domain" field to "pbi.net" and turn on the "redirect" flag
on the list, then all traffic to any of the "foobar@hookup.net" addresses
will be redirected to the corresponding "foobar@pbi.net" address, effective
the next time the aliases table gets rebuilt.
