Email plays a crucial role when running a Mastodon instance. For example, users will receive their signup confirmations or password reset links via email—and you need an SMTP server, because if those messages don’t make it to the inbox, your users will be stuck! We don’t want that to happen. And folks will want to know about new followers, too! You’ll have to make sure your Mastodon instance can send these emails fast and reliably—and you’ll need an SMTP server to make that happen.