For share access with an unjoined Windows Client this Issue also applies.
smbclient "//$(hostname -f)/faxi" -U faxuser
The access is still possible
smbclient "//localhost/faxi" -U faxuser
The access is no longer possible, if the user uses ntlm to authenticate.
Add the following lines in
/etc/samba/local.conf [global] winbind use default domain = yes