Invite users - email not working

Hi Grafana Supporters,

I am using Grafana v5.2.2 in a docker container. I tried to create new users and send out an email invite, however, the emails are not being sent by Grafana.

Following is my docker configuration setup via Ansible:
#Grafana Setup
- name: Run/Restart Grafana container
docker_container:
name: grafana
image: grafana/grafana:5.2.2
state: started
restart: yes
user: root
network_mode: host
expose:
- “3000:3000”
volumes:
- “/opt/grafana:/var/lib/grafana”
env:
GF_SERVER_ROOT_URL: grafana-url
GF_SECURITY_ADMIN_PASSWORD: XXXXX
GF_INSTALL_PLUGINS: grafana-clock-panel
GF_SMTP_ENABLED: true
GF_SMTP_HOST: email-smtp.eu-west-1.amazonaws.com:25
GF_SMTP_USER:
GF_SMTP_PASSWORD:
GF_SMTP_FROM_ADDRESS: grafana@example.net
GF_LOG_LEVEL: debug

Remaining of the env variable works perfectly though, I had even enabled debug mode log level to troubleshoot this and there is no info about emails. When I missed to mentioned the port number 25 in GF_SMTP_HOST - it gave an error. So the variables are correct but the application isn’t triggering the emails.

Please advice on this

Thanks in advance.
Best.