As described in the Report 5257, there are reasons not to be in the domain, but only the password to check on the domain. Because of this error I have to stay on version 3.0.24. By an update of the client on Windows 7, I was forced to make an update of Samba.
See also Bug Report 5257 and 6662
security=server vanished with samba 4, see release notes for details. closing this bug.