This page is just a rehash of http://support.ghost.org/mail/

Several mail options are available. Mailgun seemed interesting and was new to me.

Details here on signing up for Mailgun and finding the appropriate credentials

Once you have the mailgun credentials it is simple to add mail to the blog.

cd /var/www/travels
nano config.js

and add the following lines:

  mail: {
         transport: 'SMTP',
         options: {
             service: 'Mailgun',
             auth: {
                 user: 'postmaster@mg.two-drifters.co.uk', 
                 pass: 'secretstringfrommailgun' 
            }
        }
  },

into the production section, replacing the existing mail: {}, section

Then restart
sudo service travels start