Para obter o problema diagnosticado, usei o arquivo de log ...
less +F /var/log/auth.log
... que me disse o seguinte problema ...
Aug 29 15:11:35 debian03 sshd[14537]: User userlogin from XXX.XXX.XXX.78 not allowed because not listed in AllowUsers
Aug 29 15:11:35 debian03 sshd[14537]: input_userauth_request: invalid user userlogin [preauth]
Aug 29 15:11:36 debian03 sshd[14537]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=XXX.XXX.XXX.78 user=userlogin
Aug 29 15:11:36 debian03 sshd[14537]: pam_ldap: error trying to bind as user "cn=User Name,ou=usuarios,dc=domainname,dc=com,dc=br" (Invalid credentials)
Aug 29 15:11:37 debian03 sshd[14537]: Failed password for invalid user userlogin from XXX.XXX.XXX.78 port 13098 ssh2
Aug 29 15:11:45 debian03 sshd[14537]: Connection closed by XXX.XXX.XXX.78 [preauth]
Aug 29 15:11:49 debian03 sshd[14542]: Received disconnect from XXX.XXX.XXX.165: 11: [preauth]
A solução foi adicionar o usuário "userlogin" entre os usuários de "AllowUsers" no arquivo ...
vi /etc/ssh/sshd_config
... e reinicie o serviço ssh ...
/etc/init.d/ssh restart
Obrigado! = D