[Samba] Mount share on Synology NAS (Samba 3.6.9) as client of Samba 4.1.9 AD DC

[Lars Hanke]

I set-up a basic AD DC using samba 4.1.9 successfully. I joined my NAS 
to the domain, i.e. I saw no errors and see the users and groups of my 
AD listed in the GUI of the NAS. When I try to connect to a share of the 
NAS the following happens:

mgr at ws1:~$ smbclient -U 'AD\mgr' //nas/Test
Enter AD\mgr's password:
Domain=[AD] OS=[Unix] Server=[Samba 3.6.9]
tree connect failed: NT_STATUS_ACCESS_DENIED

A connect using the same credentials to a demo share on the AD DC itself 
works fine.

I granted read and write permissions to AD\mgr on Test on the NAS. Don't 
know what it actually does, but the GUI displays it. ;)

The behaviour from Win7 Home is similar. The demo share can be mounted, 
however AD\mgr seems to lack any privileges beyond that. The NAS share 
cannot be mounted due to permission problems.

Any idea how to troubleshoot this situation?

Thanks for your help,
  - lars.