Help how can configure and test SMTP settings using docker gitlab-ee?

How to Use GitLab Self-managed
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1

Hi all,
today we deployed GitLab self repository using Docker.
It is running now.
We used docker-compose and this is my docker-compose.yml file

version: '3.6'
services:
  web:
    image: 'gitlab/gitlab-ee:latest'
    container_name: 'gitlab01'
    restart: always
    hostname: 'gitlab.company.local'
    environment:
      GITLAB_OMNIBUS_CONFIG: |
        external_url 'https://gitlab.company.com'
    ports:
      - '80:80'
      - '443:443'
      - '2222:22'
    volumes:
      - '/mnt/docker_data/gitlab_ee/config:/etc/gitlab'
      - '/mnt/docker_data/gitlab_ee/logs:/var/log/gitlab'
      - '/mnt/docker_data/gitlab_ee/data:/var/opt/gitlab'
    shm_size: '256m'
    networks:
      pe_docker_net:
        ipv4_address: 172.18.0.2
        
networks:
docker_net:
    external: true
    name: docker_net

After that I edited “gitlab.rb” file, in my case inside “/mnt/docker_data/gitlab_ee/config” path.
I added with success LDAP integration settings and I added/edited SMTP relay settings.
I am using SMTP Relay Office365 not auth.
I am using the same configuration with other services and they are working fine.

gitlab_rails['smtp_enable'] = true
gitlab_rails['smtp_address'] = "company.protection.outlook.com"
gitlab_rails['smtp_port'] = 25         
#gitlab_rails['smtp_user_name'] = "" 
#gitlab_rails['smtp_password'] = ""
gitlab_rails['smtp_domain'] = "company.com"     
gitlab_rails['smtp_authentication'] = "login"
#gitlab_rails['smtp_enable_starttls_auto'] = true
#gitlab_rails['smtp_tls'] = true
# gitlab_rails['smtp_pool'] = false

###! **Can be: 'none', 'peer', 'client_once', 'fail_if_no_peer_cert'**
###! Docs: http://api.rubyonrails.org/classes/ActionMailer/Base.html
# gitlab_rails['smtp_openssl_verify_mode'] = 'none'

# gitlab_rails['smtp_ca_path'] = "/etc/ssl/certs"
# gitlab_rails['smtp_ca_file'] = "/etc/ssl/certs/ca-certificates.crt"

### Email Settings

#gitlab_rails['gitlab_email_enabled'] = true

##! If your SMTP server does not like the default 'From: gitlab@gitlab.example.com'
##! can change the 'From' with this setting.
gitlab_rails['gitlab_email_from'] = 'gitlab@company.com'
gitlab_rails['gitlab_email_display_name'] = 'gitlab@company.com'            
gitlab_rails['gitlab_email_reply_to'] = 'noreply@company.com'
# gitlab_rails['gitlab_email_subject_suffix'] = ''
# gitlab_rails['gitlab_email_smime_enabled'] = false
# gitlab_rails['gitlab_email_smime_key_file'] = '/etc/gitlab/ssl/gitlab_smime.key'

I am running docker gitlab-ee (I did not activate this GitLab container with license code or trial).

How can I test SMTP settings?
Thanks a lot for your help!

Best regards
Federico