We upgraded from Exchange Server 2003 to Exchange Server 2007 earlier this year.
Our Konica Minolta printers have the Scan-to-Email function
This works fine (as an anonymous user) to SMTP for internal mailbox addresses.
It doesn't work however, when you specify an external mail address.
As I recall, in Exchange Server 2003, you could specify IP addresses on the SMTP connector to allow the relay. So I created a new SMTP connector in Exchange Server 2007 with the IP addresses of my printer/copiers, but this still doesn't work.