Redmine

Hi!
I have problems testing my email configuration. I test from http://[HOME_URL]/settings?tab=notifications
I use:

====REDMINE===
Environment:
  Redmine version                3.3.3.devel
  Ruby version                   2.2.7-p470 (2017-03-28) [x86_64-linux]
  Rails version                  4.2.8
  Environment                    production
  Database adapter               Mysql2
SCM:
  Subversion                     1.6.11
  Git                            1.7.1
  Filesystem                     
Redmine plugins:
  a_common_libs                  2.3.0
  easy_gantt                     1.7
  redmine_checklists             3.1.5
  redmine_contacts               4.0.8
  redmine_people                 1.3.0
  redmine_questions              0.0.7
  scrum2b                        2.0
==== Server CENTOS 6 ====
==== configuration EMAIL ===
production:
  email_delivery: 
    delivery_method: :smtp
    smtp_settings:
        address: ***
        port: 587
        authentication: :login
        domain: ****
        user_name: ****
        password: ******

I tested different configuration options but it doesn't work. I restarted redmine every time I modified the configuration file too.
How can I solve this?
Thanks in advance

Best Regards
Paul