Hi,
We have resolved by creating duplicate ship to's for shipment addresses that are the same as the bill to address but are ordered by different departments. In some of our client sites there could be as many as 15 purchasing departments, that require separate contact details.

This is similar to Steve's suggestion, but means that you do not have to keep rekeying the email address for different purchasing departments. Having a separate email address for order confirmations is necessary, but also the contact details provided on the duplicate ship to's are also necessary.

So there already is a solution in place, if you use Ship to addresses in AR with your OE.

Best,
Brian