Multigate, nomultigate Channel Options

Multiple gateways on a single channel
The  channel option tells the MTA to perform an additional rewrite of the envelope To: address during message dequeue processing in order to determine the host to connect to for message delivery. This differs from the MTA&#x27;s normal behavior when the  channel option is not used, in which case the MTA routes the message to whatever host is specified using the   channel keyword, and to the not the host specified in the message&#x27;s To: address if   is not set.

is the default.

The recipient address is rewriten as if it were a forward-pointing header address, so  is typically used in rewrite rule templates intended to only apply during this specific rewrite operation.

There are a variety of caveats associated with using the  channel option; some of its former uses are now obsolete. The remaining usage is on LMTP channels.

See also:
 * LMTP client TCPIP channels
 * Gateway or firewall or mailhub channel options
 * Channel options