I know this question has been 'answered' before, but I cannot get it to work.
We have a front-end, back-end Exchange setup. Our front-end server is named RAHU and the back-end server is KETU.
Everything is sent from our anti-spam server (JAGANNATH) to RAHU for domain delivery. I have recipient filtering setup and yes, it is enabled on RAHU's SMTP Default Virtual Server.
If I put add an address manually in the recipient filter and send a message to that address, it will return a 550 5.7.1 code - mailbox unavailable - which is correct. If I send a message to a person not in the domain, but NOT in the manual list, I expect the same behavior. Instead, it accepts the messaage, THEN sends out an NDR. I need it to not accept any e-mail to recipients not in our active directory.