Resolution
When custom attributes are added to the Active Directory configuration for provisioning, the CN schema object name of the AD attribute must be used in the Provisioning Manager (PM) keywords.txt file. This may not match the LDAP display name shown in the AD user interface and the ADSI editor.
For example, as shown in the chart below, the display name (used in the AD UI) for Extension Attribute 1 is extensionAttribute1 while the CN is ms-Exch-Extension-Attribute-1.The entry for this attribute in the keywords.txt file must specify ms-Exch-Extension-Attribute-1, not extensionAttribute1.
The entries for the extension attributes in the keywords.txt file should look something like this:
extensionAttribute1 ms-Exch-Extension-Attribute-1 -1 1,2,26 None
extensionAttribute2 ms-Exch-Extension-Attribute-2 -1 1,2,26 None
extensionAttribute3 ms-Exch-Extension-Attribute-3 -1 1,2,26 None
extensionAttribute4 ms-Exch-Extension-Attribute-4 -1 1,2,26 None
extensionAttribute5 ms-Exch-Extension-Attribute-5 -1 1,2,26 None
extensionAttribute6 ms-Exch-Extension-Attribute-6 -1 1,2,26 None
extensionAttribute7 ms-Exch-Extension-Attribute-7 -1 1,2,26 None
extensionAttribute8 ms-Exch-Extension-Attribute-8 -1 1,2,26 None
The Microsoft website contains a good reference document showing the CN (and other attributes) of the available extension attributes.
http://msdn.microsoft.com/en-us/library/ms980473%28v=exchg.65%29.aspx