The "Network interfaces" option specifies the network interface addresses that this mail system receives mail on. By default, the software claims all active interfaces on the machine. The parameter also controls delivery of mail to user@[ip.address]. This option sets the "inet_interfaces" postfix variable.
The "Destination" option specifies the list of domains that this machine considers itself the final destination for. That does not include domains that are hosted on this machine. Those domains are specified elsewhere (see sample-virtual.cf, and sample-transport.cf).
The default is "myhostname + localhost.$mydomain". On a mail domain gateway, you should also include "$mydomain". Do not specify the names of domains that this machine is backup MX host for. Specify those names via the "Relay domains" option in 'Smtp server program -> Additional UCE controls'.
The local machine is always the final destination for mail addressed to user@[the.net.work.address] of an interface that the mail system receives mail on (see the Inet interfaces help).
Specify a list of host or domain names, /file/name or type:table patterns, separated by commas and/or whitespace. A /file/name pattern is replaced by its contents; a type:table is matched when a name matches a lookup key. This option sets the "inet_interfaces" postfix variable.
DO NOT LIST VIRTUAL DOMAINS HERE. LIST THEM IN THE TABLE->VIRTUAL ITEM INSTEAD. BE SURE TO READ THE ENTIRE VIRTUAL MANUAL PAGE.