If there is no Exchange installed in the AD then all Windows File Manager tasks fail in POA 2.6.5 with the error message 'The specified directory service attribute or value does not exist'. Additionally, existing customers cannot login to their Windows File Manager.
Since POA 2.6.5 the WinFileManager service uses AD attributes 'extensionAttribute7' and 'extensionAttribute8'. Actually, these attributes are created by Exchange during installation. So, if the Exchange is not installed in the AD domain then required attributes are absent and Windows File Manager provisioning tasks fail in POA.
1. Login on AD Domain Controller as Domain Administrator.
2. The following sub-steps are needed in case when there are more than one Domain Controller in AD:
2.1 Run adsiedit.msc.
2.2 Expand the 'Schema' folder.
2.3 Open properties of the 'CN=Schema,CN=Configuration,DC=...' folder.
2.4 Find the attribute with name 'fSMORoleOwner'. The value of this property contains name of AD Schema Master. For example, in the value 'CN=NTDS Settings,CN=AD01,CN=Servers,CN=...' the AD01 Domain Controller is the Shema Master.
3. Login to Schema Master server (in case of single Domain Controller it is the Schema Master.)
4. Upload the attached 'extensionAttributes7-8.ldf' file to Schema Master (unzip the archive).
5. Run the following command (replace in the command the string 'DC=hosting,DC=local' to the distinguished name of Windows Domain):
ldifde -i -f extensionAttributes7-8.ldf -v -c "<SchemaContainerDN>" "CN=Schema,CN=Configuration,DC=hosting,DC=local"
6. Restart MPS engine using instruction in the KB article #1851.
It may happen that Windows File Manager tasks still fail after applying the instruction above, in this case reboot MPS host, and restart the tasks again.