We're using a Debian-based spam filter called CanIt... (http://roaringpenguin.com
Our system has the ability to create a LDAP user-lookup, which it can then use to verify that the recipient address actually exists. Problem is, I have not got the faintest idea how to set this up as it asks for a lot of very confusing information. If I am not mistaken, it uses the lookup via the SMTP communication, and then simply terminates the communication if the recipient is not recognized.
Since I know that there's probably a lot of information needed, which I haven't a clue what information that will be, I'll need people to ask the right questions.
Here's what the spam filter needs for it's lookup:
LDAP Server: (I would assume this is just our AD server, which is 'Server2'
Search Filter for login authentication: (default of "(sAMAccountName=%s)")
Search Filter for streaming: (default of "(proxyAddresses=smtp:%s)"
Attribute containing stream name: (default of "sAMAccountName")
There are other fields, but I don't think they will be stuff that you'll need and I can figure those ones out on my own.
Thanks for the info... please ask if you need specific information