Anyone successfully mounted a directory from a server running MS
Services for Windows, using manual name mapping, not NIS?

I have created a directory on the windows server, but when I mount it
on AIX(5.2) whereas the owner is mapped correctly, the group is
"nobody". I cannot seem to get the group to be correct.

drwxrwxrwx 2 sefas nobody 64 May 18 16:54 nfs_dir

The group should be sefas too, which is a valid group on AIX.

I have mapped the sefas user on the Windows server to the AIX sefas
user and mapped the Users group on Windows server to the AIX sefas
group.

When I try to cd into the directory on AIX I get the error NFS access
failed for server testserver: error 7 (RPC: 1832-010 Authentication
error)

Any ideas?