The routelocal channel keyword causes the MTA, when rewriting an address to the channel, to attempt to “short circuit” any explicit routing in the address. Explicitly routed addresses (using !, %, or @ characters) are simplified.
Use of this keyword on “internal” channels, such as internal TCP/IP channels, can allow simpler configuration of SMTP relay blocking.
Note that this keyword should not be used on channels that may require explicit % or other routing.