I am planning to configure SM+Declude as my primary incoming gateway.   My mail servers include a mix of Exchange and SmarterMail.   I want to do recipient verification at the incoming gateway, because I want to reject messages rather than generate NDRs.   I don't see any options for configuring recipient verification, so LDAP verification seems out of scope.  Does SM automatically do callout verification?

What does SM do differently when the incoming gateway and the mail server are both running SM and aware that the other is running SM?   Documentation is really vague about this feature.