SMTP utilize the Active Directory LDAP service to authenticate the mailsender.
But the SBG failed to pass the Active Directory login test. The LDAP service is integrated with the Donmain Controller. When try to login with the "administrator" account, it will prompt "Invalid bind credentials".
Authentication to LDAP server unsuccessful. Invalid bind credentials. DDS error code: 800206
Bind DN should be filled as following type, for example