Normally only addresses rewritten to the local channel (that is, the l
channel on OpenVMS and UNIX or the msgstore channel on NT) are looked
up in the alias file and alias database. The
keyword may be placed on a channel to cause addresses rewritten to that
channel to be looked up in the alias file and alias database also. The
exact form of the lookup probes that will be made is then controlled by
the ALIAS_DOMAINS PMDF option; see Section 7.3.1.