We've setup a Windows 2012 R2 server as a SMTP relay server ( which is a spam Filter server )to get the emails first and then forward all emails over to our Exchange 2013 server. Our Exchange 2013 setup consists of a Mailbox and CAS server role. We have emails successfully going out, but the problem is we are not getting emails in. The emails don't appear in the "badmail" or "pickup" folders on the SMTP relay server. Please tell us what are we missing, thanks.