Does anyone know if it's possible to use the GW to Exchange connector (or
some other mechanism) so that it synchs the address books bidirectionally,
but routes messages via SMTP (not over the connector)?

If I understand correctly, if you implement the GW Exchange connector for
address book syncing, it also MUST be used for mail routing as well. We
would much prefer to use SMTP routing for message flow, and not have it go
over the connector.

Is this possible?

Or is there perhaps some other way to share email address information
between the two environments while still using SMTP for mail routing?