After moving servers for the blog off of the last host to Bitnami/AWS I had some setup to do. My biggest problem came from setting up the email details in the config.js. It took forever to get this working, and I found very little use googling 'Ghost Fastmail Config.js Settings'. Hopefully if I mention 'Ghost Fastmail Config.js Settings' enough this will shoot up the search ranking and save you some time

These will help you along your way:

"mail": {
    "transport": "SMTP",
    "options": {
        "service:": "FastMail",
        "host": "",
        "port": "465",
        "secureConnection": true,
        "requiresAuth": true,
        "auth": {
            "user": "[email protected]",
            "pass": "yourpassword"

Taken directly from Digital Faction (THANK YOU!!).

Good luck!