A long time ago I wrote an entry post about how to set up the SMTP in linux boxes using a relay system you can find the post here: Relay mail from your server without MTA. Remember that SSMTP is not a SMTP service for your system but it’s more than enough for all servers that don’t work as a mail servers. Historically Unix/Linux uses sendmail command to send system notifications but usually this mails are lost because system configurations are not completed. My advice in this sense is use SSMTP.
In the past I used to use SSMTP with a GMail account but security constraints in Google mail services make it difficult to configure today. The new alternative is set up a free Mandrill account as a relay host. Mandrill is a Mailchimp service that allows you to send a lot of emails without problems and there is a free account that allows to send up to 12.000 mails per month free, more than enough usually. If you don’t know how to set up a Mailchimp account the best option to learn how to do it is follow the support documentation it’s very good IMHO.
When you have a lot of linux machines to administer you need something fastly replicable. As you know use Ansible is a very good option. Then I developed a new Ansible role to set up Mandrill accounts to SSMTP services massively using Ansible.
The Ansible role has been uploaded here: ssmtp-mandrill and the source code of the roles is in my github. Remember to install the role in your Ansible is easy:
ansible-galaxy install oriol.rius.ssmtp-mandrill
Then you only need to create your own playbook using the role and don’t forget to setup the variables with the Mandrill account settings.