When using Directory Integration in tandem with Active Directory 2012 Global Catalog and the "Partial Attribute Set", the default Recipient Validation query string in the Symantec Messaging Gateway (SMG) of "proxyAddress" will not work. This will cause failed queries to validate recipients of messages.
Active Directory 2012 does not include "proxyAddress" as a default value in the Global Catalog Partial Attribute Set. The default query string within SMG's Recipient Validation looks for "proxyAddress" to validate recipients.
One possible resolution is to add the "proxyAddress" attribute within Active Directory so that it is able to be queried properly by SMG.
Another option is to change the default query string within the SMG's Directory Integration settings to use an attribute already included within the Partial Attribute Set.
In order to change this go to Administration > Directory Integration > Edit the available Directory Data Source > Recipient Validation > Customize query.