it would be great if multple Smarthosts could be defined, if more than 1 maildomains are used.
And each Smarthost is bound to a individual mail domain.
I think many mailservers in small locations are just setup to pull by POP3 and forward to Smarthost. And its very common, that people have multiple mail accounts, with different domains.
Also in this regards i miss a feature that the domain is not authoritive, like in Exchange.
This can be used if the server doesnt host all mailaccounts. That means, the mailserver is not responsible for all mailboxes in the domain and will forward the message to the configured Smarthost, if it will get a mail where the receiver has no local mailbox.
Otherwise the sender in the local maildomain would receive an error message, that the receiver doesnt exist.