Notes

I tried to join a Synology DiskStation running DSM 6.2 to a Windows domain. But after entering the domain settings, I received the following error message:

Connection failed. Please check your network settings.

(In german: Verbindung fehlgeschlagen. Bitte überprüfen Sie Ihre Netzwerkeinstellungen.)

The strange thing was that I wasn't able to access the SMB settings in the Synology's control panel (found under File Sharing). The SMB checkbox wasn't ticked and I received the error message mentioned above.

The solution was to upgrade to DSM 7. This fixed all the problems and I could successfully join the DiskStation to the Windows domain. Thanks to the guys at serv-u Franzke for helping me to find the solution.