how to make recipient verification with callout work between UTM 9 and Exchange 2010?

Question

Hello, 
 We are receiving a lot of emails to non existent addresses through UTM. I have Recipient Verification enabled With Callout, but it does nothing. UTM still sends the emails to our Exchange server. If the addresses doesn't exist, Exchange just issues a NDR to the postmaster account. But I want emails to be reject by UTM. 
 I'm wondering if I'm missing a configuration? On UTM, I have SMTP Protection enabled in Simple Mode. We receive emails for a couple of domain names. Is there anything that I need to configure on Exchange? I have Exchange 2010 SP3. 
 Any help is greatly appreacited! Thanks!

zaphod · Accepted Answer

have tried several times to use verification with callout.. but cant get it running correctly with exchange 2010.. 
 with an exchange 2010 sp3 its easier to use verify in active directory. configure an ad-server first and then the utm ask ad for vaild email-adresses.. works without problems.

zaphod · Answer

it should work with more than one adress.