GitLab Gmail Configuration

nano /etc/gitlab/gitlab.rb
gitlab_rails['smtp_enable'] = true
gitlab_rails['smtp_address'] = "smtp.gmail.com"
gitlab_rails['smtp_port'] = 587
gitlab_rails['smtp_user_name'] = "[email protected]"
gitlab_rails['smtp_password'] = "my-gmail-password"
gitlab_rails['smtp_domain'] = "smtp.gmail.com"
gitlab_rails['smtp_authentication'] = "login"
gitlab_rails['smtp_enable_starttls_auto'] = true
gitlab_rails['smtp_tls'] = false
gitlab_rails['smtp_openssl_verify_mode'] = 'peer'
gitlab-ctl reconfigure

References
https://docs.gitlab.com/omnibus/settings/smtp.html