Do i have to install postfix on my omnibus-gitlab in order to send mails through gmail?

Hello!! I installed Gitlab CE Omnibus Package on Ubuntu 16.04 droplet. Im a newbie in all respects on mail and smtp. On the gitlab page it says that you can configure Gmail by editing the /etc/gitlab/gitlab.rb file with this:

 gitlab_rails['smtp_enable'] = true
 gitlab_rails['smtp_address'] = "smtp.gmail.com"
 gitlab_rails['smtp_port'] = 587
 gitlab_rails['smtp_user_name'] = "account@gmail.com"
 gitlab_rails['smtp_password'] = "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'

I did that and then sudo gitlab-ctl reconfigure

But it’s not sending any emails. Should i have postfix or manage some sort of certs also?

Thanks in advanced.