Interfaceaddress Channel Option

TCP/IP interface address
The  channel option controls the address to which a TCP/IP channel binds as the source address for outbound connections; that is, on a system with multiple interface addresses this channel option controls which address will be used as the source IP address when the MTA sends outgoing SMTP messages. Note that it complements the Dispatcher option   (INTERFACE_ADDRESS in legacy configuration), which controls which interface address a TCP/IP channel&#x27;s SMTP server program listens on for accepting incoming connections and messages. Also note that such channel  settings are quite separate from the Job Controller&#x27;s own    setting  (INTERFACE_ADDRESS setting in legacy configuration), which merely controls what IP address the Job Controller listens on for purposes of its own, internal communications.

As of MS 8.0.2.3 two different addresses, one used for logging and the other as the actual TCP/IP source address, can be specified. Normally the same address is used for both purposes, but in cases where NAT or other forms of address translation are in use it may be useful to have the actual IP address that appears to external agents appear as the address in transport information fields in the logs. The address that&#x27;s actually used does need to be logged somewhere, so it is appended to the application information field with the usual "/" separator, prefixed with a sharp sign.

When two addresses are specified they must be separated by a sharp sign with the logging address appearing first, i.e., "logging-address#bind-address".

See also:
 * TCPIP channels
 * listenaddr Option
 * TCPIP connections and DNS lookups channel options
 * Channel options
 * port Option